WIP:  Content Experiments Documentation

See draft documentation at:  http://draft-nested-components.readthedocs.org/en/latest/organizing_course.html#nested-components
I'm trying to figure out what the staff actually gets done by using this feature, and I'm not coming up with much -- they can't monitor student work, or use it to learn who's in what group... Are they testing the different content options? maybe retitle to reflect that use: Test a Content Experiment?  
or maybe make the tile parallel to some of the sections we have on The Student View of X: The Staff View of Content Experiments?