Modified the remove_section method to pass parameters via POST, instead ...

This pull request contains a change to the remove_section method's signature. Modified the remove_section method to submit the parameters via a regular form POST, instead of the current  url replace in a javascript. Found an issue with the old implementation while doing a similar change in add_people_to section.
Changes include:
1)view.py - method change
2)urls.py 
3)test.py- modified the test case with new signature  and a couple mthods to test for missing section and sis_section_id
4)create_secton_form: modified ajax call to submit the formdata