Python 3 Compatibility & Travis CI Integration

Hey there Yiorgis, hope you're doing well :smile: 

Great library you have here.  I've spent the afternoon making it Python 3 compatible and adding a Travis CI config so we can easily see the build status.

A few little notes about this pull request:

- PyPy is intentionally not included in the Travis configuration.  I spent today also porting Splinter to Python 3 and can confirm that it doesn't work with PyPy at the moment due to an lxml issue which causes a Segmentation fault.
- bootstrap.py is updated directly from http://downloads.buildout.org/2/bootstrap.py

Please let me know if you have any questions mate.

Cheers
Fotis