Use edx namespace for Backbone classes
Add tabs to the cohort editor
Create a RESTful handle_cohort view method for GET and PUT/POST.
Share form between new modal and settings
Implement full new/save support for cohorts
Fix unit tests
Fixes server bug and allow renaming of random cohorts.

Still needs unit test for renaming of random cohorts.
Do not support renaming of random cohorts (to be squashed).
Adjustments to markup and styles from PR review
Missed a comment in the PR review, removed unused classname
Don't allow renaming of cohorts
Changing classname of individual form field items
Using convention for is-hidden
Updating markup to use form-field instead of the plural
Adding one more wrapper for form-field
Sass refactor and cleanup
Fixing conflicts on merge; added JS from pull
Fixing conflicts in JS file
Adding screen reader friendly text to active tab