Preparing v1.5.4 release

[smmaurer]

This PR prepares the v1.5.4 release, a compatibility update to support PyToolz 0.11+ and resolve deprecation warnings in Pandas and core Python.

A more substantial v1.6 release will follow (see issue #48), but we wanted to get this out quickly because the PyToolz issue (#50) breaks Orca in certain environments.

Included in this PR

• added Python 3.8 to the Travis script
• removed doc building from the Travis script, per current UDST-wide workflows
• updated version numbers to 1.5.4
• added an entry to the change log
• affirmed support for Python 3.9 in the setup.py metadata (ran tests locally and they pass)
• added doc building instructions (adapted from Pandana)
• updated installation section of docs
• moved "building the Orca UI JS bundle" instructions from GitHub readme to the docs
• expanded the project description in the GitHub/PyPI readme

Release steps

• [x] build and upload docs
• [x] upload release to pypi
• [x] update the conda-forge recipe
• [x] confirm installation works
• [x] finalize on GitHub

[coveralls]

Coverage remained the same at 96.606% when pulling 36d62c9522df75536503fdfc30a83a3891fa7e02 on release-prep into 1d320788b3a716206f5b37e186da0d827e2e9f29 on dev.

[coveralls]

Coverage remained the same at 96.606% when pulling 36d62c9522df75536503fdfc30a83a3891fa7e02 on release-prep into 1d320788b3a716206f5b37e186da0d827e2e9f29 on dev.