v0.3.1: Bug fixes required for PUDL data release

A couple of minor bugs were found in the preparation of the first PUDL
data release:
* No maximum version of Python was being specified in setup.py. PUDL
  currently only works on Python 3.7, not 3.8.
* epacems_to_parquet conversion script was erroneously attempting to
  verify the availability of raw input data files, despite the fact that
  it now relies on the packaged post-ETL epacems data. Didn't catch this
  before since it was always being run in a context where the original
  data was lying around... but that's not the case when someone just
  downloads the released data packages and tries to load them.

v0.3.0: 2020 Q1 PUDL release in support of data archiving

This release is mostly about getting the infrastructure in place to do
regular data releases via Zenodo, and updating ETL with 2018 data.

Added lots of data validation / quality assurance test cases in
anticipation of archiving data. See the pudl.validate module for more
details.

New data since v0.2.0 of PUDL:
* EIA Form 860 for 2018
* EIA Form 923 for 2018
* FERC Form 1 for 1994-2003 and 2018 (select tables)

We removed the FERC Form 1 accumulated depreciation table from PUDL
because it requires detailed row-mapping in order to be accurate across
all the years. It and many other FERC tables will be integrated soon,
using new row-mapping methods.

Lots of new plants and utilities integrated into the PUDL ID mapping
process, for the earlier years (1994-2003).  All years of FERC 1 data
should be integrated for all future ferc1 tables.

Command line interfaces of some of the ETL scripts have changed, see
their help messages for details.

v0.2.0: Data package based output without PostgreSQL

This is the first release of PUDL to generate data packages as the
canonical output, rather than loading data into a local PostgreSQL
database. The data packages can then be used to generate a local SQLite
database, without relying on any software being installed outside of
the Python requirements specified for the catalyst.coop package.

This change will enable easier installation of PUDL, as well as
archiving and bulk distribution of the data products in a platform
independent format.

v0.1.0: Reference release of PUDL using PostgreSQL

This is the only release of PUDL that will be made that makes use of
PostgreSQL. It is provided for reference, in case there are users
relying on this setup who need access to a well defined release.

v0.1.0rc1: RC1 for PostgreSQL based legacy PUDL release

v0.1 of PUDL will be the only release we make of the PostgreSQL based
system, mainly for archival / reference purposes, in case there are
users who need to be able to install this version to support their
existing systems while transitioning to the datapackage / SQLite
version, which will be released within the next couple of days as v0.2

v0.1.0a4: Fixed Windows console UTF-8 encoding issue.

Output from the pudl_setup script was generating an unprintable
character on the Windows console, causing a UnicodeEncodingError,
revealed by the conda-forge tests. This release fixes that output.

v0.1.0a3: Updated/simplified specification of dependencies.

The previous release used extras_require in setup.py to specify a couple
of packages required for dealing with parquet files. This prevented the
parquet functionality from being available after a "vanilla" pip install
of the package, which was confusing for test users. The parquet packages
have now been added to install_requires, and compilation issues were
worked around by making their installation conditional in the
readthedocs build.

v0.1.0a2: Removed dependencies unavailable on conda-forge.

In order to be able to distribute this postgres dependent version of
PUDL on conda-forge, we needed to remove the one remaining dependency
that wasn't available for installation via conda,
sqlalchemy-postgres-copy. This version should be buildable on
conda-forge.

v0.1.0a1

PUDL pre-release that builds a local PostgreSQL DB