Use external prop-types package

[dmcclory]

Hi!

I'm using react-stepzilla, but I'm encountering these warnings:

Warning: Accessing PropTypes via the main React package is deprecated. Use the prop-types package from npm instead.

They're pretty trivial, but they're messing up my CI runs.

I checked the source and noticed that stepzilla is importing PropTypes from react, which is in the process of being moved into that external package.

I can put up a PR if you'd like!

[newbreedofgeek]

@dmcclory the latest version of React moved PropTypes to its own package:
https://facebook.github.io/react/blog/2017/04/07/react-v15.5.0.html

I'll probably bump up the packages React version today and try and push a new version of StepZilla, stay tuned...

[newbreedofgeek]

@dmcclory I've upgraded to react 15.5.4 and pulled out PropTypes to use prop-types npm.

This should get rid of the warning messages now. Please let me know if you have any other issues.

New build has been published to npm, so make sure you update to v4.5.0

[newbreedofgeek]

@dmcclory closing as I've not heard anything and assume it worked.