Fix bug 938332 - Point mentors at mailing list sign-up

Previously, contributors who signed up would be directed to send email
to a moderated mailing list. Now we will direct them to sign up for the
mailing list first.
[bug 935164] Update CTA for Montenegro Fx OS page
Merge pull request #33 from mozilla/bug-935164-update-cta-for-montenegro

[bug 935164] Update CTA for Montenegro Fx OS page
[fix bug 944750] Missing OpenStreetMap attribution
Merge pull request #1464 from alexgibson/bug-944750-missing-openstreetmap-attribution

[fix bug 944750] Missing OpenStreetMap attribution
Merge pull request #1460 from jbuck/edu-resp

Fix bug 938332 - Point mentors at mailing list sign-up