Advbumpversion

- add --tag-name option
- now works on Python 3.2, 3.3 and PyPy

- bugfix: Read only tags from `git describe` that look like versions

- bugfix: ``--help`` in git workdir raising AssertionError
- bugfix: fail earlier if one of files does not exist
- bugfix: ``commit = True`` / ``tag = True`` in .bumpversion.cfg had no effect

- **BREAKING CHANGE** The ``--bump`` argument was removed, this is now the first
positional argument.
If you used ``bumpversion --bump major`` before, you can use
``bumpversion major`` now.
If you used ``bumpversion`` without arguments before, you now
need to specify the part (previous default was ``patch``) as in
``bumpversion patch``).

- add --no-commit, --no-tag

- If available, use git to learn about current version