Allow `results` and `autosave` attributes (WebKit/Blink)

WebKit/Blink supports the non-standard attributes `results` and `autosave` for input-elements of type `search`.

They allow the input element to be rendered as a search input (looking glass is added), allows the ability to show a list of recent searches, and also makes it possible to autosave the value of the field - [more info here](http://www.wufoo.com/html5/types/5-search.html).

React currently do not pass these attributes on, and I have not found a way of adding the attributes except in the `componentDidMount`-method. I'd prefer to have some way of adding these attributes inside of the react world, so the server and client can generate them.

I realize that adding all sorts of non-standard attributes might eventually pile up - perhaps there is a better way of adding these attributes? `<input nonStandardAttributes={{ results: 5, autoCapitalize: false }}>` or similar?

Nits:
- ABC order in this groups
- Let's make it `autoSave` like we've done for the other `auto*` properties. You'll need to then add the uppercase to lowercase mapping farther down as well.