Add a view helper to render react component.
Introduce react_ujs.

* Implement react_ujs.
* Replace inline scripts with react_ujs style data attributes.
* Update tests and README.
Update JSXTransform test case, fix travis test.

Newer coffee-script generates slightly different output, accept it
in JSX coffee script test case.
Address issues about empty props.

* react_ujs: use `null` instead of `{}` as default props.
* view helper: remove 'data-react-props' if props is empty.
* view helper: allow 'data' in HTML options.
Set `eval` context to `window`.

This allows better minification.
Implement server rendering