Add python 2.6 in our tests

We currently have tokens for `py26-*` but we haven't enabled `2.6` in our python list so we're only testing against `2.7`.

![screen_shot_2014-08-11_at_3_40_40_pm](https://cloud.githubusercontent.com/assets/494338/3881649/8ef54cfc-218f-11e4-8037-fd54e3a77a62.png)