The command "tox -e docs" to build documentation failed with several
errors with the following messages:
doc/source/contributing.rst:4:Problems with "include" directive path:
InputError: [Errno 2] No such file or directory: '../CONTRIBUTING.rst'.
doc/source/usage.rst:document isn't included in any toctree
This patch fixes it to successfully build documentation.
Change-Id: I6fc144881a1a92ae44e2ff5b5be9c3c5de005523
068e995c92