Upgrades to use React v0.12

This simply makes the minimal changes necessary to comply with the new React v0.12 guidelines (eliminates all warnings when using then un-minified version of 0.12). Not sure if the bower/package.json files need changing; I'll leave that up to you. This is my first ever pull request for a public project, so if I did anything wrong please forgive me :)

Thanks for this great component!