Therefore, hardcoded sha's are not allowed anymore, as the contents of
the repository is unknown.

Fixes #16, for real this time ;)

I have verified that all tests are working, even without a parent
git repository, as long as the said environment variable is set.

Fixes #16

autopep8 -v -j 8 --max-line-length 120 --in-place --recursive

With a bit of luck, this one will just work now.

This fixes most of the import errors that came from using the
implicit relative imports that Python 2 supports.  This also fixes
the use of `xrange`, which has replaced `range` in Python 3.  The
same has happened for `izip`, which is also being aliased.

The octal number syntax changed in Python 3, so we are now
converting from strings using the `int` built-in function, which
will produce the same output across both versions of Python.