Fix for #3

This is a bit of a hacky solution, as the comment explains, but it's the
simplest way of providing code equivalence between Python 2 and 3. I'm
beginning to see what Armin Ronacher is on about with regard to Python
3's insistence upon your-filesystem-will-be-unicode-or-else!
Merge branch 'master' of github.com:waveform80/picamera