Improve `html` styles
Improve `html` styles

Summary:When the browser is narrower than `.container` or taller than the content, `<html>` `background-color` is visible:

<p align="center">
  <img src="https://cloud.githubusercontent.com/assets/220979/13725333/ff857572-e863-11e5-92bf-33f8626014cc.png" width="400">
</p>

_You can also see this issue if you decrease the browser’s zoom level._

**Changes:**
- De-dupe the `html` selector
- Move `body` `background-color` to `html`
- Remove `body` rule
- :abc: `html` properties
Closes https://github.com/facebook/draft-js/pull/201

Differential Revision: D3045903

fb-gh-sync-id: 53a4b4f211fb3329f33ed7e1054b51c8fd7d703d
shipit-source-id: 53a4b4f211fb3329f33ed7e1054b51c8fd7d703d

brookslyrette/draft-js,SciMts/draft-js,johnmpotter/draft-js,tonygentilcore/draft-js,johnmpotter/draft-js,davidchang/draft-js,brookslyrette/draft-js,dirkholsopple/draft-js,facebook/draft-js,dirkholsopple/draft-js,tonygentilcore/draft-js,davidchang/draft-js,TripleDip/draft-js,SciMts/draft-js,TripleDip/draft-js