Make Travis use py 3.4 + fix in find_font

was: OMG tests fail if I run locally

* in util/image.py we try to set a string into a byte object
* in ext/freetype.py (line 36) we are using `.encode('utf-8')
  on a byte object.

Maybe this is because I use Python 3.4? If this is the case, we need to add a Travis machine for 3.4.