Add modules option 'register' as default output format name

Move the test-interpret-throw test after mocha, so we can trace while testing

Add unit test for src/node/api.js

Symptom: bizzare error messages when using options {modules: false, blockBinding: true}.
Analysis: Block binding is not supported in Modules and modules: false
is not correctly handled.
Here we add tests and fix part of the modules false issue.

Partial fix for #595

Review URL: https://github.com/google/traceur-compiler/pull/901

Closes #901.