Some cleanups in stats

Playing with PyCharm, may as well get it to do something semi-useful....

This is mainly:

- PEP8 fixes
- changes in docstrings (imports) to conform to numpy doc standard
- removing extraneous parenthesis
- changing to in-place operations where possible

Hmm, I now get 0.075413401.. Not sure what happened, I just copy pasted the output and with another seed the results are much more different. Will update.