Notify HipChat of "make jstest" failures

Summary:
The jobs website-commit and website-allcheck now use the changes from
http://phabricator.khanacademy.org/D6619

When make emits "make: *** [jstest] Error <FAILURE COUNT>" we extract a
subset of failure information and send it to HipChat.

JavaScript test output is contained in genfiles/jstest_output.txt. Lines
with one leading tab are test titles, lines with two leading tabs are
the failing condition, and lines with three leading tabs are the stack
trace (we ignore these).

Test Plan:
Fingers crossed. Once there are failing JavaScript tests, they should be
messaged in HipChat like failing Python tests and lint failures.

Reviewers: csilvers

Reviewed By: csilvers

Differential Revision: http://phabricator.khanacademy.org/D6629