Convert to Python3

[ralic]

using : find . -name '*.py' | xargs 2to3 -w

[philipkershaw]

Thanks for this Ralic. The changes look straightforward. I'd prefer to keep the code dual 2 and 3 compatible if possible. I've done this with some other similar packages using six. I'll take a look but can't promise to do straight away. It you feel like trying yourself in between times it would be much appreciated.