Add teachers and students report to main site. Also had to change pygeoip submodule link to avoid permission issues.

Summary:
add links to teachers dashboard

image for main page for teachers and studendt report

change url of pygeoip submodule

Test Plan: dashboards.khanacademy.org shows teachers and students growth link

Reviewers: jace, chris

Reviewed By: chris

Differential Revision: http://phabricator.khanacademy.org/D2582