Initial implementation of pep257 tool.
Added pep257 to the no_doc_warnings profile.
Bumped pep257 version to one that isn't broken.
Merged upstream changes.
Merge cleanup.
Added pep257 to docs.
Merge pull request #51 from jayclassless/pep257_tool

Pep257 tool
Merge branch 'master' of ssh://github.com/landscapeio/prospector
Fixing turning tools on or off
[refs #31] Adding support for checking single files
Updating changelog with several new features and bug fixes
Fixing unit test to match new behaviour for deciding whther a tool is enabled or not