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.

This is possible thanks to @stefanpenner , @yapplabs, and @mhelabs for the idea and awesome work behind RSVP's instrumentation and the Promise Inspector.

- [x] Create promise tree tab
- [x] Create PromiseDebug which will use the Promise Assembler in @stefanpenner's Promise Inspector
- [x] Finish and merge RSVP [inspection branch](https://github.com/stefanpenner/rsvp.js/tree/inspection) into master. Merged: https://github.com/tildeio/rsvp.js/pull/137
- [x] Re-integrate with RSVP
- [x] Add timing info
- [x] Add label info to promises in Ember Data ([PR Merged](https://github.com/emberjs/data/pull/1578))
- [x] Add label info to promises in Router.js ([PR Merged](https://github.com/tildeio/router.js/pull/62))
- [x] Add label info to promises in Ember.js core ([PR Merged](https://github.com/emberjs/ember.js/pull/3946))
- [x] Make the inspector backwards compatible with Ember versions that don't support instrumentation.
- [x] Use top sorted array instead of recursion for rendering the tree
- [x] Optimize performance by removing observers in promise_debug and using list-view for the tree
- [x] Add a button to trace the promises by sending the stack trace to the console. 
- [x] Add stack trace to RSVP instrumenation events ([PR merged](https://github.com/tildeio/rsvp.js/pull/177))
- [x] Ember Debug PromiseAssembler unit tests
- [x] Ember Debug Promise Integration tests
- [x] Promise tab Integration tests
- [x] Fix issue with promise assembler being initialized after initial route is handled ([RSVP PR Merged](https://github.com/tildeio/rsvp.js/pull/183))
- [x] Make Firefox inject ember_debug before DOM ready /cc @rpl
- [x] Figure out which icon best represents Promises to use on the Promise nav item (@nummi is working on it)
- [x] Re-label Router.js promises after the refactor.