update react and add proptypes as dependency

[phoebeschmidt]

since React 15.5 PropTypes has been moved into its own library.
https://reactjs.org/docs/typechecking-with-proptypes.html

I'm trying to use this plugin with React v.16.0 and it's incompatible.

[alexandraclaire]

I am also having this problem - it would be good to get a fix because it's a great idea.

[eberhara]

Hey @phoebeschmidt @alexandraclaire

I am planning to fix this as parte of v2. There is a branch where I am working on it.

[eberhara]

@alexandraclaire @phoebeschmidt v2 is on!
Now it supports both react 15 and 16.

Thank you!