Move assert out of traceur.js into its own module.

The goal is to make traceur.js have no logic in it.

Review URL: https://github.com/google/traceur-compiler/pull/342

Closes #342.
Forgot to git add assert.js
Remove getModuleForTesting

Review URL: https://github.com/google/traceur-compiler/pull/343

Closes #343.
Merge branch 'master' into module-path

Conflicts:
	bin/traceur.js
	src/codegeneration/module/ModuleVisitor.js
	src/runtime/modules.js
	src/semantics/symbols/Project.js
Cleanup/fix merge issues
Everything works
Remove new-modules option
cleanup