Update create testenv

[ColCarroll]

This would have caught #2227, and should catch pip install pymc3 issues in the future. I'm not sure what the effects of installing everything with pip instead of conda are, but we'll see. I've marked it WIP since there might be a merge conflict adding h5py to requirements.txt, as in #2228.

[ferrine]

pymc3 runs nice on py3.6. Why do we force <3.4?

[kyleabeauchamp]

I think this is because Enum34 is only needed for py34, but not needed for py35 and py36.

[ferrine]

ok

[ColCarroll]

yeah, I'd be surprised if anyone was actually using python 3.3 or 3.2 at this point, but figured we'd allow for that :) More realistic would be python_version <= 2.7

[ColCarroll]

Should be ready to go once tests pass.

Not sure if it was the problem, but a test (the ARM5_4 example, I think) was timing out (i.e., over 10:00) until I installed numpy, scipy, and mkl-service with conda. It passed last time at ~7mins, which is still ~1min longer than other jobs right now. I have to assume that's because it is using the pip installed theano, instead of installing from mater.