Get rid of the python-hipchat library.

Summary:
It wasn't really making our lives any easier.  The hipchat API now
lets you specify rooms by name, not ID, which obviates the biggest
advantage the lib was giving us.

(I took the hipchat-sending code from alertlib.)

Test Plan:
Ran a dev-appserver and visited
   http://localhost:8080/admin/test_send_to_hipchat
and logged in as an admin.  It said 'OK', and the HipChat Tests room
successfully got a message from snippet-server.

Reviewers: alpert, chris

Reviewed By: chris

Differential Revision: http://phabricator.khanacademy.org/D12881