Fixed to pick up site specific styles

Fixed to pick up site specific styles
Remove redundant warning related to issue #1044

Not sure if this can be closed but the video page already gives a
noscript warning - removed the redundant warning that shows up
temporarily even when you have javascript enabled
refactor fake_remote_grader, use context manager (#1730)

In order to support other kinds of remote grader failure modes, useful
to abstract that functionality into something more general.  Created an
abstract base class (by convention only).

Implement this as a context manager to ensure that the urllib2 cleanup
happens for me.  Cleaner and more reliable.
interactive tests: factor xml out and share (#1730)
interactive grader tests: three failure modes (#1730)
interactive autograder: retry logic, handle more exceptions (#1730)
interactive autograder: more precise watchword checks (#1730)
quizdown for MC and SA
Merge branch 'master' of https://github.com/Stanford-Online/class2go into jbau-quizdown
Quizdown with video assoc
small tweaks
mathjax rendering for previewing explanations
migration + code for saving import quizdown
actually add migration
remove unneeded import
moved remove() call for aElem after all references
some examples/support for surveys -- resp w/o ans
better slugs if things are small
Merge pull request #2114 from Stanford-Online/sef-1441-db-router

Read-only database support (#1441)
Merge pull request #2113 from uwacsp/dglance-fixes

Fixed to pick up site specific styles