Vcspull

- :issue:`300` Update libvcs to 0.4.0, also fixes :issue:`298` issue on initial checkout
- :issue:`301` Move from Travis to GitHub Actions

- :issue:`231` Add updating / merging of remote URLs (via PR :issue:`297`)
- Fix colorama constraint
- poetry lockfile: Fix (accidentally pushed lockfile via prerelease
version of poetry)

- Fix pyproject.toml libvcs pin

- Fix pyproject.toml release version
- Fixes to contribution docs

- :issue:`257` - Move from Pipfile to poetry
- Removed dependency on releases for CHANGES, use plain reStructuredText
for now
- Loosen constraints for colorama
- Update click to 7/8
- Add `project_urls` to setup.py

- Sort imports
- Add isort package, isort configuration in setup.cfg, and
`make isort` task to Makefile.
- Add `make sync_pipfile` for updating _Pipfile_
dependencies against _requirements/\*.txt_ files.
- Update Pipfile
- Package updates

Base / Core dependencies:

- kaptan: 0.5.9 to >=0.5.9,<1 (adds Python 3.7 compatibility)
- pyyaml: >=3.12,<4 (adds Python 3.7 compatibility)

Docs:

- sphinx: 1.7.1 to 1.7.5
- alagitpull: 0.0.19 to 0.0.21