Include sample configuration in dev docs

Since including the sample configuration in tree is
becoming difficult to maintain, lets try moving it to
the developer docs. We still have the ability to view it
easily for users, and it can be auto-generated on doc build,
so it should also always be up to date.

Change-Id: I7ec2d76448feef5ecb9af7c238bbd12619fa31d8
diff --git a/.gitignore b/.gitignore
index 1777cb9..043de00 100644
--- a/.gitignore
+++ b/.gitignore
@@ -18,3 +18,4 @@
 .coverage*
 !.coveragerc
 cover/
+doc/source/_static/tempest.conf