Power Analysis Module

**Not ready for merge**

The module imperially estimates the power of a dataset using Monte Carlo simulation. The functions take test, a function which accepts a list of sample ids or values, and returns a p-value.

In conjunction with Statsmodels, the code can be used to generate power curves, for a sufficiently large number of samples. (Depending on the effect size, about 20 - 30 in each group).

Pre-merge issues
* Documentation

This is why tests are failing, and I think it should be removed (starting in line 58) b/c ctrl-f can't find plotting here, right?