With thanks to Tanvi Moharir, Ashutosh Varma, Benjamin Rüth, Lucas Jansen,
Timothy Lusk and Barret O'Brock for contributions.

* Respect `versionfile_source` in `__init__.py` snippet (#241)
* Add `pep440-branch` and `pep440-post-branch` styles (#164)
* Stop testing deprecated `easy_install`, support left in for now (#237)
* Use `versionfile_build` instead of `versionfile_source` where needed (#242)
* Improve handling of refname edge cases (#229)
* Clarify installation in docs (#235)
* Play nicely with custom `build_ext`s (#232)