Add more context to Theano / pymc3 hack
Add more context to Theano / pymc3 hack

Also disable saving wheel caches on docker image.

berkeley-dsep-infra/datahub,ryanlovett/datahub,ryanlovett/datahub,berkeley-dsep-infra/datahub,berkeley-dsep-infra/datahub,ryanlovett/datahub