Move the documentation from the wiki into pldoc

[shonfeder]

Currently, the most detailed documentation lives this repo's wiki. We should probably move this in to the pldoc instead, so it will be available in the package's documentation.

[Anniepoo]

I just did the inverse with pack(identity).

I had all the docs in the readme. In particular, I had an ambitious 'roadmap'.
It complicated making branches to work on features, because the docs kept getting updated.

[shonfeder]

Isn't updating docs and merging in those changes just part of the development process? :) I'm a pretty big believer in keeping the documentation as close to the code as possible, since it makes it easier to keep things synced.

[Anniepoo]

Good argument. you're the boss here.