Remove external dependency on "js-bundle".
Make async runner use "then" method instead of "chain".

I think that because of the problems inherent with "then", there is a good
chance that ES7 will ultimately use "chain", but since native promises in
non-V8 environments do not have it, we have to adapt.
Use readable param names for the async wrapper function.
Support generic iterables in array destructuring.
Add preliminary tests for ES6 shims.  Much more work to be done.