Implement TA reassignment

[scriptbae]

In the original implementation, the TA assignment mechanism was incomplete client-side. This is to be implemented after major parts of #12 are complete.

The interface should consist of, at least:

• A dropdown for course selection;

• A dropdown for section selection; and

• A dropdown for TA selection.

Comments are welcome about additional features which may be useful.

[scriptbae]

@NuclearBanane @inspectorG4dget any input re: additional features?

[scriptbae]

Closed by PR #52.