Make compatible with python 3

[eric-wieser]

What are your thoughts about using a package like six to make the work on both major python versions?

I'm happy to have a stab at implementing this, but it may come at a slight readability cost.

I'm assuming that you very much want to keep python 2 support.

[mitchgu]

Feel free to give it a shot.
The main motivations for python 2.7 are: 1. I'm more familiar with it and 2. pypy's version of numpy doesn't support python 3. I'm using numpy for a pretty trivial thing though, so the second point is probably easily overcome.

I just tested the benchmark on the winbook and cpython gives a throughput that is around 50-60% that of pypy. 1770 packets/s vs 2968 packets/s. Both are probably acceptable but I do like keeping the pypy support. Unfortunately both are like 5-6 times slower than on my OSX machine. This is probably why.