Working on integrating options from oslosphinx theme

- First patch only modifies tox.ini to add an html-only
  build option to iterate quickly.
- Modify .gitignore for working on Mac OSX locally.

Next patches in series will take care of:
- Adds a Project-only search form in bottom of left-hand navigation bar
  Trying to differentiate between project-scoped search and broad
  site search.
- The "Project Home page" link renamed from "Contents" in nav.
- Build number now available in lines "Updated" also is
  displayed. Shows a bulleted list with "Current" if that is the
  only available version. Seems to have a lot of space, okay?
- Add a link to project source in sidebar.

Change-Id: Ic71c1f7c17048c521fce4b08989b0c57c175e043

.gitignore

@@ -3,6 +3,7 @@ _build/
 /ChangeLog
 /dist/
 /openstackdocstheme.egg-info/
+.DS_Store
 *.pyc
 doc/build
 doc/source/BBresult

tox.ini

@@ -29,6 +29,12 @@ commands =
   make -C doc/build/pdf
   sphinx-build -a -E -W -d api-ref/build/doctrees -b html api-ref/source api-ref/build/html
 
+[testenv:html]
+commands =
+  rm -rf doc/build api-ref/build
+  python setup.py build_sphinx
+  sphinx-build -a -E -W -d api-ref/build/doctrees -b html api-ref/source api-ref/build/html
+
 [testenv:releasenotes]
 commands =
   rm -rf releasenotes/build