Setting Prepend initially.

Experimental.
Selecting a random prompt on init
Prompt driver added.

Only iterates up, need to change functionality for iteration.
Small bug fixes on prepends
First build of prompt iteration.

Two separate ng-clicks for up and down iteration. Not idea. A ton of
repeated code. :/
Refactored iterate prompt

Now only one fuction that accepts a parameter to determine math type.
Added missing placeholder text.
cleanup is post_controller
Deleted Prepend Controller.

Not needed.