Add a copy of the Google Closure Compiler

Means we can continue to build on any machine that we check out on
without having to install additional software or modify the Makefile.
Which is nice.
Use the checked-in copy of the closure compiler.

Changed the makefile to call tools/closure-compiler/compiler.jar instead
of assuming you got it installed already in a fixed location relative to
your home dir.
Syntax fix in src/states.js

I was writing the functions as (e.g.)

  StateMachine.prototype.foo(bar)

when it should have been

  StateMachine.prototype.foo = function (bar)