python 3.3+ compatiblity

[stonebig]

Hello,

I see you wrote python 2.7 in your requirements.
Do you know of something avoiding this to work with python 3.3+ ?

[mwaskom]

Honestly I have remained fairly ignorant about Python 3 compatability, and expect that will remain the case for at least a little while as I have various things keeping me tied to 2.7 for my own work. With that said, I'd certainly rather have Seaborn work on 3.3+ than not, I just don't really have the bandwidth to both learn how to maintain 2&3 code and keep up with it. So, pull requests would be very welcome!

[mwaskom]

Closed with #46