Fix Demo so it builds against NUIParse

This PR adds NUIParse to the Podfile and includes the Pods folder so that users can play with NUI without installing CocoaPods.

When we have a [real test suite and project](https://github.com/tombenner/nui/issues/48) for NUI, we should change the demo to not include NUI directly in the source tree, but rather install NUI (and therefore NUIParse) via CocoaPods.