Bug 865058 - fix newsletter ordering

* Fix sorting of newsletters on /existing page so they're sorted by
  the newsletters' `order` field
* Add a test
Bug 896232 - Make newsletter form localizable
Merge pull request #1093 from TheoChevalier/newsletter-form-localizable

Bug 896232 - Make newsletter form localizable
Merge pull request #1080 from dpoirier/bug-865058-fix-newsletter-ordering

Bug 865058 - fix newsletter ordering
Update firstrun A/B templates (phase 2 testing). Bug 881207.
Fix bug 862842 - Add Webmaker Mentor list signup to /contribute

When users sign up on https://mozilla.org/contribute and select "Education"
from the drop down list, an additional checkbox to sign up for the Webmaker
Mentor mailing list should appear.
Merge pull request #1086 from jbuck/contribute
Merge pull request #1098 from mozilla/bug-881207-firstrun-phase1-round2

Update firstrun A/B templates (phase 2 testing). Bug 881207.
Bug 896001 Aborted GA Call on Newsletter Submission
Merge pull request #1099 from alexgibson/aborted-ga-call-on-newsletter-submission-bug-896001

Bug 896001 Aborted GA Call on Newsletter Submission