WIP on String.prototype[@@iterator]; Github issue #539
Use maybeAddIterator
Insert repl options at top of file based on user's choices.

Also rely less on global options.
Fixes #1213.

Review URL: https://api.github.com/repos/google/traceur-compiler/issues/1219

Closes #1219, closes #1213.
Array.from polyfill: Only use Function#call when thisArg is provided.

This was much slower than it needs to be for the common case, when `thisArg` isn't provided.
Switch to use import * as for code

This removes the support for the old syntax

Fixes #1119