PEP8 reformatting

Converted comments to docstrings, and (very minor) changes to variable
names, paretheses, spacing, tabs, etc.
Updated setup.py

Multi-line description now with triple quotes
Added faster allan variance calculation method

Added a file that compares the avar_series() code I wrote against
the adev() code in allantools. They are equivalent, except the
numpy use in avar_series() gives it a ~60x speedup.

This is not yet a replacement for adev() as it doesn't handle
timestamps /sampling rates in the same way.
Merge pull request #3 from telegraphic/master

PEP8 compliance and a faster adev() method