Update to React 15

[geirsagberg]

aspnet-webpack-react currently uses React 0.14, which leaves data-reactid-attributes all over the output. Updating to v 15 will fix this, and some other issues (https://facebook.github.io/react/blog/2016/04/07/react-v15.html).

[SteveSandersonMS]

Sounds good! Would you be able to submit a pull request?

[geirsagberg]

Yup, see #256.

[SteveSandersonMS]

Thanks - closing in favour of #256

[geirsagberg]

A quick note; seems the react-id-attributes are still there in React 15 when calling renderToString, as they are needed to connect the client code. Still, updating to React 15 shouldn't have any adverse effects.