Install pyprof2calltree which lets us profile python programs with cachegrind.

Summary: I also install qcachegrind (OS X) / kcachegrind (linux).

Test Plan: Fingers crossed.

Reviewers: alan

Reviewed By: alan

Differential Revision: http://phabricator.khanacademy.org/D6869
Put editor directive in .bashrc.khan instead

Review: csilvers