* Mark transpiled JSX elements as pure
* Avoid duble annotation
* Add "pure" option to the React preset
* Fix generator indentation
* Update tests
* Add tests for the "pure" option
* Update windows fixtures
Given the following
```js
a = <F new/>
```
We used to generate:
```js
a = React.createElement(F, {"new": true})
```
but now we generate
```js
a = React.createElement(F, {new: true})
```
If you need to quote these (ie for ES3 you can use
transform-property-literals)
* Use helper-builder-react-jsx inside plugin-transform-react-inline-elements.
This avoids duplicating the logic for converting jsx elements to plain JavaScript.
* Add a comment which explains the _jsx signature, [skip ci]
so it is a little bit easier to understand what all those .splice() calls do
