Use https for all github urls.
Use https for all github urls.

Summary:
Addresses https://app.asana.com/0/25429045350268/219824402827972

I have no idea if this is necessary, but I'm guessing it can't hurt.

Test Plan: None

Reviewers: emily, jared

Reviewed By: emily

Differential Revision: https://phabricator.khanacademy.org/D36986

learningequality/perseus,learningequality/perseus,ariabuckles/perseus,ariabuckles/perseus,ariabuckles/perseus,ariabuckles/perseus