Packaging improvements

[webknjaz]

Hi, have you considered using setuptools-scm plugin?

It'd automagically replace git ls-files logic in setup.py and it can also add a single source of truth for storing dist version.
With it, you'd use Git tags and wouldn't have to manually hardcode the version in two places https://github.com/libgit2/pygit2/blob/master/pygit2/_build.py#L40 / https://github.com/libgit2/pygit2/blob/master/.travis.sh#L5.

[webknjaz]

https://github.com/pypa/setuptools_scm

[webknjaz]

@jdavid ^

[jdavid]

Sounds good, will you make a PR?

[webknjaz]

okay