Based on yapf (https://github.com/google/yapf) this
formatter currently only works with --full.  It defaults
to pep8 style and projects that use a different style
can add .style.yapf to the top level.

Review URL: https://codereview.chromium.org/1156743008

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@295547 0039d316-1c4b-4281-b951-d872f2087c98