This updates PycodestyleTool to subclass the newer BaseTool, and to use

the newer features it offers (dependencies, improved centralized base

command building, and standardized error code/column output).
The output from pycodestyle is now explicitly set, so we won't be

susceptible to any changes in pycodestyle in the future.
Unit tests were added to cover the new parsing, and to peform

integration testing with the command line tool.

Unit tests pass on Python 2.7 and 3.x.