Staging v3.2 release

[smmaurer]

This PR prepares for the v3.2 release.

For a list of substantive changes included in the release, see issue #218 and the prior PR (#225).

Changes in this PR:

• Updates copyright year in license and docs
• Updates version numbers in setup, init, and docs
• Revises the main README
• Updates docs: intro and installation
• Fixes and documents the doc building procedure
• Updates contribution guide to match other UDST repos
• Renames HISTORY to CHANGELOG and adds entry for this release
• Removes cruft (outdated scripts, old settings for coverage and pep8)
• Fixes a numpy deprecation

Testing:

• Unit tests are passing on Mac (local), Linux (travis), and Windows (appveyor)
• For integration testing, I'm running the MTC model with urbansim 3.1.1 and 3.2, with a consistent random seed, to see if it completes successfully and if all of the results match

Next steps:

• Merge this to dev
• Release on PyPI
• Set up conda-forge feedstock
• Update the live docs
• Merge to master
• Tag release in GitHub

[coveralls]

Coverage decreased (-0.4%) to 93.945% when pulling 80225d4 on release-prep into 57c82bd on dev.