Renames SAI to DAI and SKR to PETH.

DEVELOPING.md

@@ -30,8 +30,8 @@ and reference implementation, is strongly encouraged but not required.
 Sai uses the following tokens:
 
 - `gem`: underlying collateral (wrapped ether, in practice)
-- `skr`: abstracted collateral claim
-- `sai`: stablecoin
+- `peth`: abstracted collateral claim
+- `dai`: stablecoin
 - `sin`: anticoin, created when the system takes on debt
 
 Sai has the following core components:
@@ -52,28 +52,28 @@ Sai is configured by the following 'risk parameters':
 
 
 
-### `skr`: A Token Wrapper
+### `peth`: A Token Wrapper
 
-`skr` is a token wrapper.
+`peth` is a token wrapper.
 
-- `join`: deposit `gem` in return for `skr`
-- `exit`: claim `gem` with their `skr`.
+- `join`: deposit `gem` in return for `peth`
+- `exit`: claim `gem` with their `peth`.
 
 ![Join-Exit](https://user-images.githubusercontent.com/5028/30517891-928dd4d8-9bc1-11e7-9398-639233d851ae.png)
 
-`skr` is a simple proportional claim on a collateral pool, with the
-initial `gem`<->`skr` exchange ratio being 1:1.  The essential reason
+`peth` is a simple proportional claim on a collateral pool, with the
+initial `gem`<->`peth` exchange ratio being 1:1.  The essential reason
 for this abstraction will be developed later, but for now it is
-sufficient to see `skr` as a token with intrinsic value.
+sufficient to see `peth` as a token with intrinsic value.
 
-The `gem`/`skr` exchange rate is called `per`, and is calculated as the
-total number of deposited `gem` divided by the total supply of SKR.
+The `gem`/`peth` exchange rate is called `per`, and is calculated as the
+total number of deposited `gem` divided by the total supply of PETH.
 
 The reference price of `gem` (in practice, ETHUSD) is provided by the
 `pip`, an external oracle. The `pip` is completely trusted.
 
-The reference price of `skr` is then given by the dynamic `tag`, e.g.
-the price of SKR in USD.
+The reference price of `peth` is then given by the dynamic `tag`, e.g.
+the price of PETH in USD.
 
 
 ### `vox`: Target Price Feed
@@ -99,7 +99,7 @@ The `tub` is the CDP record system.  An individual CDP is called a `cup`
 (i.e. a small container), and has:
 
 - `lad`: an owner
-- `ink`: locked SKR collateral
+- `ink`: locked PETH collateral
 - `art`: debt
 
 It is crucial to know whether a CDP is well collateralised or not:
@@ -122,8 +122,8 @@ to unsafe:
 ![Lock-Free](https://user-images.githubusercontent.com/5028/30517892-928e06ec-9bc1-11e7-91e8-6ae6caae8585.png)
 
 
-- `lock`: deposit SKR collateral (increases `ink`)
-- `free`: withdraw SKR collateral (decreases `ink`)
+- `lock`: deposit PETH collateral (increases `ink`)
+- `free`: withdraw PETH collateral (decreases `ink`)
 
 ---
 
@@ -164,52 +164,52 @@ its allowed behaviour:
 
 - `joy`: Sai balance, surplus transferred from `drip`
 - `woe`: Sin balance, bad debt transferred from `bite`
-- `fog`: SKR balance, collateral pending liquidation
+- `fog`: PETH balance, collateral pending liquidation
 
-and one derived price, `s2s`, which is the price of SKR in Sai. The
+and one derived price, `s2s`, which is the price of PETH in Sai. The
 `tap` seeks to minimise all of its token balances. Recall that Sai can
 be canceled out with Sin via `heal`.
 
 The `tap` has two acts:
 
-- `boom`: sell Sai in return for SKR (decreases `joy` and `woe`, decreases SKR supply)
-- `bust`: sell SKR in return for Sai (decreases `fog`, increases `joy` and `woe`, can increase SKR supply)
+- `boom`: sell Sai in return for PETH (decreases `joy` and `woe`, decreases PETH supply)
+- `bust`: sell PETH in return for Sai (decreases `fog`, increases `joy` and `woe`, can increase PETH supply)
 
 `boom` is the simpler function and can be thought of as buy and burn.
-Given a net Sai balance, sell the Sai in return for SKR, which is
+Given a net Sai balance, sell the Sai in return for PETH, which is
 burned.
 
 <img src="https://user-images.githubusercontent.com/5028/30517887-924bec1c-9bc1-11e7-8c25-6d73a1c48340.png" width="500" />
 
 `bust` is really two functions in one: collateral sell off (aka `flip`),
 and inflate and sell (aka `flop`). When `fog` is non zero it is sold in
 return for Sai, which is used to cancel out the bad debt, `woe`. If
-`fog` is zero but the `tap` has a net Sin balance, then SKR is minted
+`fog` is zero but the `tap` has a net Sin balance, then PETH is minted
 and sold in return for Sai, up to the point that the net Sin balance is
 zero.
 
 ![Bust](https://user-images.githubusercontent.com/5028/30517888-9287dd76-9bc1-11e7-8726-6b21843e27a5.png)
 
 Through `boom` and `bust` we close the feedback loop on the price of
-SKR. When there is surplus Sai, SKR is burned, decreasing the SKR supply
-and increasing `per`, giving SKR holders more GEM per SKR. When there is
-surplus Woe, SKR is inflated, increasing the SKR supply and decreasing
-`per`, giving SKR holders less GEM per SKR.
+PETH. When there is surplus Sai, PETH is burned, decreasing the PETH supply
+and increasing `per`, giving PETH holders more GEM per PETH. When there is
+surplus Woe, PETH is inflated, increasing the PETH supply and decreasing
+`per`, giving PETH holders less GEM per PETH.
 
-The reason for wrapping GEM in SKR is now apparent: *it provides a way
+The reason for wrapping GEM in PETH is now apparent: *it provides a way
 to socialise losses and gains incurred in the operation of the system.*
 
 Two features of this mechanism:
 
-1. Whilst SKR can be inflated significantly, there is a finite limit on
+1. Whilst PETH can be inflated significantly, there is a finite limit on
    the amount of bad debt the system can absorb - given by the value of
    the underlying GEM collateral.
 
-2. There is a negative feedback between `bust` and `bite`: as SKR is
+2. There is a negative feedback between `bust` and `bite`: as PETH is
    inflated it becomes less valuable, reducing the safety level of CDPs.
    Some CDPs will become unsafe and be vulnerable to liquidation,
    creating more bad debt. In an active market, CDP holders will have to
-   be vigilant about the potential for SKR inflation if they are holding
+   be vigilant about the potential for PETH inflation if they are holding
    tightly collateralised CDPs.
 
 
@@ -220,7 +220,7 @@ system and reimbursing Sai holders. This is provided for easy upgrades
 between Sai iterations, and for security in case of implementation flaws
 - both in the code and in the design.
 
-An admin can use the `top` to `cage` the system at a specific price (sai
+An admin can use the `top` to `cage` the system at a specific price (dai
 per gem), or by reading the last price from the price feed.
 
 <img src="https://user-images.githubusercontent.com/5028/30519069-6c9ae656-9be1-11e7-9e3f-e75f585024f7.png" width="600" />
@@ -232,16 +232,16 @@ call.
 
 ![Cash](https://user-images.githubusercontent.com/5028/30519070-6cc4fd6a-9be1-11e7-92d8-5d965721d8ef.png)
 
-Any remaining `gem` remains in the `tub`. SKR holders can now `exit`.
+Any remaining `gem` remains in the `tub`. PETH holders can now `exit`.
 CDP holders must first `bite` their CDPs (although anyone can do this)
-and then `free` their SKR.
+and then `free` their PETH.
 
 Some important features of `cage`:
 
 - Sai holders are not guaranteed their face value, only preferential payout.
-- *the full real collateral pool is tapped* to make Sai whole. SKR is a
+- *the full real collateral pool is tapped* to make Sai whole. PETH is a
   *risk-bearing* token.
-- SKR holders will receive a poor rate if they try to `exit` before all
+- PETH holders will receive a poor rate if they try to `exit` before all
   CDPs are processed by `bite`. To prevent accidental early `exit`,
   `top.flow` is provided, which will only enable `exit` after all CDPs
   are processed, or a timeout has expired.
@@ -294,8 +294,8 @@ Sai is designed with two authorities, `dad` and `chief`.
 
 - `dad` is a DSGuard, and is used for internal contract-contract
   permissions, allowing e.g. the `tub` to `mint` and `burn` Sai. `dad`
-  is the authority of the `tub` and `tap`, and also `sai`, `sin` and
-  `skr`.
+  is the authority of the `tub` and `tap`, and also `dai`, `sin` and
+  `peth`.
 
 - `chief` restricts access to `top` and `mom`, which are the admin
   interfaces to the system. `chief` is intended to be a DSRoles
@@ -336,12 +336,12 @@ bin/deploy
 
 ### Prices
 
-- `per`: gem per skr
-- `par`: ref per sai
-- `tag`: ref per skr
+- `per`: gem per peth
+- `par`: ref per dai
+- `tag`: ref per peth
 - `pip`: ref per gem
-- `fix`: gem per sai after `cage`
-- `fit`: ref per skr after `cage`
+- `fix`: gem per dai after `cage`
+- `fit`: ref per peth after `cage`
 
 ### Meme Mnemonics
 
@@ -358,9 +358,9 @@ bin/deploy
 - `axe`: penalty applied to bad CDP holders
 - `gap`: gap between buy and sell
 
-- `pie`: Real collateral that SKR holders share
+- `pie`: Real collateral that PETH holders share
 - `air`: Abstracted Collateral backing CDPs
 - `ice`: Debt that is locked up with CDPs
 - `fog`: Murky liquidated `air`that we want to get rid of
-- `joy`: SKR holders are happy about this Sai surplus
-- `woe`: SKR holders are sad about this Sin debt
+- `joy`: PETH holders are happy about this Sai surplus
+- `woe`: PETH holders are sad about this Sin debt