enable compatibility with react 12.0

I’ve avoided using the jsx-loader since version 0.12.0 calls `this.callback` just like jshint-loader leading to a conflict.
Instead I’m using the react tools directly to transform the source.
Merge branch 'v0.12' of https://github.com/danielberndt/jsxhint-loader into danielberndt-v0.12

Conflicts:
	package.json
Merge branch 'v0.12' of https://github.com/danielberndt/jsxhint-loader

Conflicts:
	package.json
Merge branch 'danielberndt-v0.12'