fix log spew from ReactDOMInput test

The prop validation threw a warning that either `onChange` or `readOnly` is required. Set the `onChange` where needed.
fix log spew from ReactDOMTextarea test

Similar to previous but for textarea. If `value` is set, we have to also set
`onChange` to avoid warnings.
better error message for React EventPlugin order check

Ran into this while inadvertently requiring multiple React versions in a separate project (`require('react');` vs `require('React');`