Change Nav headers to green
New condensed layout with sphinx formatting.
Content and styling can be previewed here - http://fabric-rtd.readthedocs.io/en/latest/


The overall objective was to consolidate and still clearly
delineate the important sections & topics.  This should act as a
conduit for developers to more easily contribute.
[ci-skip]

Change-Id: Ie13a5dcfa8cca95e7ef47c746685d996050feaca
Signed-off-by: Nick Gaski <ngaski@us.ibm.com>