Libvcs

- Fix issue with subprocess.Popen loud warning on Python 3.8
- [296] - Move from Pipfile to poetry
- Sort imports
- Add isort package, isort configuration in setup.cfg, and `make isort` task to Makefile.
- Add `project_urls` to setup.py

[296] https://github.com/vcs-python/libvcs/pull/296

- Move vcspull to the vcs-python organization
- Fix issue where VCS objects failed to set attribute in Ubuntu 18.04.

- Update documentation to point to libvcs.git-pull.com
- Switch doc theme to alabaster
- Pin and update libraries via pyup
- update vulture 0.8.1 to 0.11
- update flake8 from 2.5.4 to 3.2.1
- update pytest-mock from 1.4.0 to 1.5.0
- update pytest from 3.0.4 to 3.0.5
- pin alabaster to 0.7.9
- pin sphinx to 1.5.1

- Fix bug with unused `support` module in vcspull. See [vcspull43]

[vcspull43]: https://github.com/vcs-python/vcspull/pull/43

- Update pytest to 3.0.2, remove unused pytest-raisesregexp dependency.
- Fix bug in `which` when executable is not found. Allow specifying search paths manually.
- Better support for missing VCS when testing on git and subversion.

- [9] Support for `progress_callback` to use realtime output from commands in progress (such as
`git fetch`).
- [9] More tests, internal factoring and documentation, thanks jcfr
- [9] Official support for pypy, pypy3
- [11] : Fix unbound local when updating git repos

[9]: https://github.com/vcs-python/libvcs/pull/9
[11]: https://github.com/vcs-python/libvcs/pull/11