Python3 support

### What is the problem / feature ?

It'd be nice if flex worked on python 3

### How did it get fixed / implemented ?

Added python3 support and testing against python 3

### How can someone test / see it ?

install flex in python 3?


*Here is a cute animal picture for your troubles...*

![il_340x270 525368121_5vtn](https://cloud.githubusercontent.com/assets/824194/5135908/fa65afa4-70db-11e4-80d2-6b02d81e0012.jpg)