Destructuring does not require an object any more
0.0.57
Remove runtime remove assertObject

This could not be included in the last commit due to self hostin
issues. It required a npm push before it was safe to remove.
Correct sourceMaps option in test and verify it.

Partly fixes #1254

Review URL: https://api.github.com/repos/google/traceur-compiler/issues/1258

Closes #1258, closes #1254.
Add Options.diff and refactor test to use it

Set Options through setOptions to check for unknown options.
Correct sourceMap -> sourceMaps
Fixes #1254