Add new prop-types package.
Add new prop-types package.

Next update of react will require some refactoring: https://github.com/facebook/prop-types#prop-types, https://reactjs.org/blog/2017/04/07/react-v15.5.0.html#migrating-from-react.proptypes

howlround/worldtheatremap,howlround/worldtheatremap