Feature/additional tests (part 2)

* adds tests for function assign_track_and_create_student, other controller methods, new model methods, and adds two more tests to cover all of experiment_pages
* note: this is Part 2 of feature/additional_tests.


Might be helpful to add a test description here.  I had to read through to understand that the test fails due to the number of weights in the list being < number of tracks.