dillon1000/react

Fix up Perf a bit better for 0.13

_mountImageIntoNode moved into ReactMount and wasn't being counted where it was supposed to be. In addition, all DOM elements are now wrapped in a composite wrapper but for the perf tools we want to skip over those or else we'll double-count (at least with the current accounting -- and that's effectively what we did before so this brings us back up to parity).

Fixes #3407.

Test Plan:
Used the jsbin from #3407 and saw similar output from this branch and 0.12:

![image](https://cloud.githubusercontent.com/assets/6820/6649816/4d7202e0-c9b2-11e4-9364-e1b50c96b55b.png)