Production build should not include proptypes definitions

[jochenberger]

The proptypes specifications should be stripped from the production build.
The definitions could be wrapped in if (process.env.NODE_ENV !== 'production') clauses, but that won't get replaced in the browserify bundling step.
That probably makes it a feature that could go into https://github.com/JedWatson/react-component-gulp-tasks, but it might be a better idea to switch to Webpack or even Rollup on the long run. @JedWatson, any advice how this should be solved?

[jochenberger]

Since the build uses rollup now, it might be a good time to revisit this.