Use "https://" instead of "git://" for anoymous GitHub requests in documentation
Summary: These both work, but "git://" uses a nonstandard and possibly firewalled port, is less familiar to users, and is not promoted in the GitHub UI.
Test Plan: grep, reviewed diff.
Reviewers: chad, avive, avivey
Reviewed By: avivey
Subscribers: epriestley, avivey
Differential Revision: https://secure.phabricator.com/D9360