Setup testing for python 3.3 support
python 3.3 port (same sourcecode support 2.6/2.7/3.3)

Used the same method as in flask, importing compat stuff from
flask._compat.

Changed requirements to also fetch werkzeug from git as it otherwise
fetches a non-py33 compatible version.

All tests succeed for 2.x, there is still 1 strange failure left on 3.3
that seems somehow unrelated to the changes done for the port.
Fix compatibility with current Flask HEAD
Fix bad rebase of master onto python3 branch
Merge branch 'master' into python3
Minor .travis.yaml cleanup
Various cleanups
Merge branch 'python3'