stored benchmarks work in python2 but not python3

[zingale]

pyro simply uses pickle to store the output, since this is easy to implement, but it is not portable. The test benchmarks were output with python3, and they are in its pickle format. As a result, python2 cannot unpickle them. This discusses some of the issues:

http://stackoverflow.com/questions/28218466/unpickling-a-python-2-object-with-python-3

Potential solutions are

• convert to h5py to write out a portable output file. This is probably best in the long run, but will add another dependency and require a read routine and reinitialization routine to give the features that unpickle does for us

• have 2 benchmarks directories, 2/ and 3/, storing the python2 and python3 output respectively.

[zingale]

this is no longer an issue since we use h5py now