Bug 1419772 - [docs] Enable the sphinx.ext.napoleon extension, r=gps

This enables sphinx to parse both the google and numpy style docstring
formats which tend to be more human readable than the default sphinx
format.

See:
http://www.sphinx-doc.org/en/stable/ext/napoleon.html

MozReview-Commit-ID: REmZ4IoUG8

--HG--
extra : rebase_source : 4e3e788d09a7fcc3d3e84bb94744019583e1ee5e

tools/docs/conf.py

@@ -36,6 +36,7 @@ sys.path.insert(0, OUR_DIR)
 extensions = [
     'sphinx.ext.autodoc',
     'sphinx.ext.graphviz',
+    'sphinx.ext.napoleon',
     'sphinx.ext.todo',
     'mozbuild.sphinx',
     'sphinx_js',