Debugging Promises WIP

This is still work in progress.  Adds a "Promise" tab to the inspector and displays a tree of Promises along with helpful debug info.

- [x] Create promise tree tab
- [ ] Create PromiseDebug which will use the Promise Assembler in @stefanpenner's Promise Inspector
- [ ] Move Promise Assembler into its own repo
- [ ] Finish and merge RSVP [inspection branch](https://github.com/stefanpenner/rsvp.js/tree/inspection) into master
- [ ] Add label info to promises in [Ember Data](https://github.com/emberjs/data)
- [ ] Add label info to promises in [Router.js](https://github.com/tildeio/router.js)
- [ ] Figure out which icon best represents Promises to use on the Promise nav item
- [ ] Complete test coverage for all of the above

![promise_debug](https://f.cloud.github.com/assets/1061742/1486870/9eaafe02-472a-11e3-8bbf-23c0dd705976.png)