doc: initial sphinx-based documentation support

The release-notes script now produces Markdown compatible with
pandoc to help convert it into RST for sphinx.

Actual documentation is fairly limited currently.

We use intersphinx to link to various sub-projects' docs.

A .travis.yml file is added to build+publish documentation
when new code is pushed to github.

Signed-off-by: Stewart Smith <stewart@linux.vnet.ibm.com>
diff --git a/doc/requirements.txt b/doc/requirements.txt
new file mode 100644
index 0000000..085b3a7
--- /dev/null
+++ b/doc/requirements.txt
@@ -0,0 +1,2 @@
+sphinx
+recommonmark