We expect goal authors to edit goals/template.txt as
reStructuredText and save as a new file with a .rst suffix, so we
should give the template that suffix as well for clarity. Add it to
the exclusion list so that Sphinx won't mind.
Change-Id: Ied69b10a64a715b89cc3ee72f544c8525a25a4d7
4985ca2e2e