Add 'git weekly' to show all the changes you've made since last monday.

Summary:
This is intended to help with writing snippets.

Rewrite nginx.conf to point to khan/webapp, not khan/stable.

stable is dead.  Long live webapp!

Test Plan:
Ran manually in khan/webapp, saw it gave only my commits since April 22.

Fingers crossed

Reviewers: alpert

Reviewed By: alpert

Differential Revision: http://phabricator.khanacademy.org/D2169