Upgrade RSVP

- instrumentation hooks for tooling
- still promise/a+ 2.0.2 compliant
- adds support for finally/catch
- adds documuncation
- perf
- cleanup
- several fixes
- no longer brings it's own async, as we just use use back burner.


Also
- upgrade loader to support relative module paths
restore sync assertions. This will hopefully help in failure
scenarios, and prevent aging.

Now that we ship with a default RSVP.on('error', ... ) that raises
awareness, promise swallowed assertions should be no more.