Adds integration tests for word_cloud module
change from_xml class method on video class to make sure we honor the fact that the xml string could actually be a pointer to another file on disk which actually contains the attributes
Use Backbone notifications for course section delete.
Use Backbone notifications for component delete.
Use Backbone notifications for setting graded status.
Factor out common code between module editing and course overview.
Studio: changed the copy and prompt type for unit + outline deletions
Remove `@xhr.restore()` to fix tests.
Remove commented-out code and add test.
PDF uploader dialog refers to "PDF" instead of "asset"
PDF Upload button now refers to "PDF" rather than "asset"
Link section to course outline
Trim whitespace when adding course authors.
Make XModuleDescriptor use the XBlock children API

N.B. When we are in a world of mixed XModules and XBlocks, the
system/runtime will have to be cognizant of that when asked to return a
XModule from an XModuleDescriptor child

[#LMS-190]
formatting
make sure parsed times are set to UTC
convert datetime.now() to datetime.now(UTC) for xqueue
convert all datetime.now() to datetime.now(UTC)
Merge pull request #41 from edx/alex/word_cloud_course_factory

Word cloud tests
Merge pull request #462 from edx/cale/use-xblock-children-api

Make XModuleDescriptor use the XBlock children API