Update mover.js per Khan conventions

It turns out I can't make comments on files, just commits, so I'm doing this as a commit, which I can undo if you'd like.
The changes are that I declared the constructor using the var Bla = syntax, which is the only way we support declaring functions on Khan.
I also added semi-colons to the end of the function declarations, as we also require those and they are best practice since those are indeed statements.