Support ES7 rest properties in destructuring

This adds support for ES7 rest properties in the ES6 destructuring. This is
kind of lame since the ES6 destructuring takes on a dependency on the ES7 one
but it simplifies things since the ES6 destructuring isn't really composable.

Currently the helper function is inlined on every use. I don't expect this to
be used very much yet so this is probably fine until we have a runtime or
recast.
Exclude node 0.8 from travis builds :(
Add note to readme to direct new users toward Recast
Update README.md
6.1.0
Point at esprima 6001.1.0-dev-harmony-fb
Add type syntax strip-out visitors
6.2.0