Feature/sections tool sm2

This pull request contains changes for delete section" 
- added remove_section method that uses canvas_sdk
-prevent primary sections from being deleted
- added ajax call to UI to handle 
    *hide the deleted row on success
    * display success and failure message
    * display special message when primary section is attempted to deleted(even though UI doesn't have a delete for primary sections)
- unit tests
- UI has a 2 delete icons as placeholder -one for deletable sections and a disabled one when member count >0

I'm not understanding what this test is doing. The comment says it's looking for a success status code, but it sets a 400 (bad request) as the return code?
Also, I see remove_section in there twice and it's unclear what response is doing.