Make React editor backward compatible with find-and-replace marker views

Fixes #2343

Had to detect whether the view was an editor using a class check rather than `instanceof` in `find-and-replace` and add 3 shim methods. We should still switch `find-and-replace` over to marker views but it's no longer a blocker for switching.

![screenshot 2014-05-23 18 57 52](https://cloud.githubusercontent.com/assets/1789/3073231/6040706e-e2e0-11e3-90d3-56c312cdb4db.png)