Update callbacks reference to include the EditorState
Update callbacks reference to include the EditorState

Summary:
**Summary**
These 4 `Editor`'s properties: `handleReturn`, `handleKeyCommand`, `handleBeforeInput` and `handlePastedText` now also pass the latest editor state.

This is a follow up on #1371.

**Test Plan**
Go to `/docs/api-reference-editor.html#cancelable-handlers-optional` and check the method's signatures include the editorState.
Screenshot:
<img width="677" alt="screen shot 2017-09-08 at 11 07 23 am" src="https://user-images.githubusercontent.com/78122/30225168-55aab596-9486-11e7-82e6-ee3d6ce9c79d.png">
Closes https://github.com/facebook/draft-js/pull/1374

Reviewed By: sophiebits

Differential Revision: D5804964

Pulled By: sophiebits

fbshipit-source-id: 29a03e8b0e0af419eebbf11a01bfa7145407311c

facebook/draft-js