Remove setuptools 2to3 hook.
Port the minimal needed to get the test suite to run in python3.
Support reading packs from io.BytesIO

(io.BytesIO rasises a io.UnsupportedOperation when calling it's .fileno() method)
Skip tests in python3 that fail (most of them :-()
Enable testing python3.4 on travis.
Make a note in README that the Python3 port is ongoing.
Avoid using dulwich._compat for Python3 porting.
Merge branch 'python3'.

This improves python3 support and makes the testsuite pass by basically
disabling most tests on Python3.

This is still a work in progress. DULWICH DOES NOT YET SUPPORT PYTHON3.