initial using subseconds
Fixes #1568 sub-second timing for questions

One bug fix:
@sefk the fix in exams/views.py/update_score wasn't quite right,
was bombing on multiple-choice, but is now fixed

@wescott because I checked the submit button to be static, and
removed "survey-submit", I had to fix C2G.checkSubmitStatus().
I also changed the fadeTo transitions to 'fast', since it seemed
like questions that were closely spaced were not working.  (not that
we'd often have those anymore)
New commit fixes #1690 clicking thumbnail when video stopped

Also fixes #1772 layout weirdness with child items when in-video
question is shown
Merge pull request #1770 from Stanford-Online/jbau-subsecond

Jbau subsecond