Test option.freeVariableChecker

module-loader needed to bail and report errors in transformers.
Magically options.types results in options.freeVariableChecker??

Fixes #492

Review URL: https://github.com/google/traceur-compiler/pull/509

Closes #509, closes #492.
Add makefile targets bin/tracer-runtime.js and bin/traceur-runtime.min.js

Also target 'concat' to build bin/traceur.js by concatenating bin/traceur-runtime.js and a compile without a runtime.
The concat target can be tested to verify separate compilation.

Review URL: https://github.com/google/traceur-compiler/pull/513

Closes #513.
Change super binding to start with Class.prototype (or Class for statics)

The super calls should start with `Class.prototype` (or `Class` for static methods)

Fixes #511

Review URL: https://github.com/google/traceur-compiler/pull/512

Closes #512, closes #511.
Remove protoParent argument to createClass

Now that super starts with the `Class.prototype` we do not need to keep protoParent in scope. We can therefore remove the argument and just use a local variable inside `createClass`.

Review URL: https://github.com/google/traceur-compiler/pull/514

Closes #514.