Add basic gitignore

Ignore .pyc and __pycache__

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
Add python3 support

This allows running the code using python3 as well as python2.

Tested basic UI functionality with python2.7 and python3.4.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>