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

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

By default, a small repository will be tested, which doesn't take that long actually (~20s)
Additionally, that way we enforce correctness tests, which didn't run by default previously.
As we are handling data here, we must be sure that it's handled correctly, thus the tests should
run.

Conflicts:
	gitdb/base.py
	gitdb/fun.py
	gitdb/pack.py
	gitdb/stream.py
	gitdb/test/lib.py
	gitdb/util.py

range in py2 will return a list, which can mean a lot of time and memory
is spent on generating it even though it's just used for iteration.

Simplified implementation of MAXSIZE

This changes the internals to use BytesIO over StringIO, which
fixed a few of the failing tests in Python 3.  We are only
importing from `io` now, instead of the entire chain, as this is
available in Python 2.6+.

In Python 3, the default string type is now the Python 2 unicode
strings.  The unicode strings cannot be converted to a byte stream,
so we have to convert it before writing to the streams.

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.