Add send-to-graphite support to *all* the gae-scraping scripts!

Summary:
We now have a utility file to do this work since three different
scripts need to do it.

Test Plan:
Set up the various secrets in my homedir and ran
   env srcdir=. username=prod-deploy@khanacademy.org ./fetch_stats.sh -v
and saw it complete successfully.

Reviewers: chris

Reviewed By: chris

Differential Revision: http://phabricator.khanacademy.org/D8364