Fix pep8 violations

Fix/cale/gradebook

It was added to 2 different locations by mistake.

Don't try to export orphaned draft items.

#278

Update with 2013-04-10 changes

Grading works when sequence is loaded from saved state

fixing the visual display of the stanford logo 

fixing the visual display of the stanford logo used in press releases on the homepage and dashboard (proportions were off)

Fix/vik/sa and coe

cope with ErrorModule as source (or required) module, and add tests.

add documentation for HTML textbook

Properly save and restore settings.MODULESTORE, and clear at django._MODULESTORES at the end of the test

Disable nps survey in test environment