Updated openstack/openstack
Project: openstack/heat  531e95a6cc5065f1b1cb71b87fe93f94281d69a3

Edits on template_guide/functions.rst

Edits for consistency:
* Fix spelling and capitalization
* Add missing "."
* Use same layout for "Returns"

Change-Id: Ieb2effc1f45fb261f45775be9664ea93b04c8e98