Add tests for all features from Traceur wiki

This commit adds tests for array comprehension, arrow functions,
classes, computed property names, default parameters, destructuring
assignment, iterators and `for of`, generator comprehension,
generators, modules (currently commented out until the Loader API is
fixed in Tracuer), numeric literals, property method assignment, object
initializer shorthand, rest parameters, spread, template literals, and
promises. All tests are copied from http://git.io/Z1loOg and were only
modified if absolutely necessary. All modifications are commented.