Automated HAR capture for Studio

Collect page load information in HAR files for Studio via bok choy tests.

STUD-2028
@dan-f  https://github.com/edx/bok-choy/pull/53 merged...  so this should be good to move forward.  You'll have to update the hash to 9162c0bfb8e0eb1e2fa8e6df8dec12d181322a90 though.