Try to use default python on Trusty, for speed
Try to use default python on Trusty, for speed

Running `pyenv install` wastes about 3 minutes.

* https://docs.travis-ci.com/user/languages/python

    "for Trusty, this means 2.7.6 and 3.4.3"

Streamlet/GoogleHelper,Streamlet/GoogleHelper,Streamlet/GoogleHelper,Streamlet/GoogleHelper,Streamlet/GoogleHelper