Move 'prop-types' to peerDependencies about mobx-react-devtools

[andykog]

I don't like adding another peerDependency for this plus It's not the recommended way: https://github.com/facebook/prop-types#how-to-depend-on-this-package (see also facebook/prop-types#4)
So I've simply updated prop-types and removed definition of NODE_ENV (it was shipped with NODE_ENV=production)
Released as 4.2.13
@le0nik, @bernex, could you confirm that the warning is gone?

[bernex]

Warning: Failed prop type: Calling PropTypes validators directly is not supported by the prop-types package. Use PropTypes.checkPropTypes() to call them.

same error with last version....

[le0nik]

@andykog can confirm that it's fixed in 4.2.13

[bernex]

@andykog confirmed!