separate AlphaRenamer from ScopeTransformer base class
Report ModuleEvaluationError via .message.
Unfortunately seems like Node prints Error.message rather than Error.toString().
Compile kangax's es6 tests and verify the compat-table entries.

The compat-table data-es6.js file builds the web page showing compatiblity results.
Reading that file and extracting the tests allows tracuer results to be verified.

Review URL: https://github.com/google/traceur-compiler/pull/1164

Closes #1164.
Correct whitespace and type test in verify-compat from #1164

Review URL: https://api.github.com/repos/google/traceur-compiler/issues/1167

Closes #1167.
Improve error messages from getProtoParent.

Extend coverage to cover super prototype not an object.

Review URL: https://api.github.com/repos/google/traceur-compiler/issues/1158

Closes #1158.