look up the new kinds of constructors generated by purescript

New to PureScript, but I was playing around and wanted to get this working with the latest build of the PureScript compiler (see https://github.com/purescript/purescript/pull/454 for the change that seems to break `prop.ctor`). Seems to work, but I don't know if there are edge cases I'm missing or something. Feel free to hold off on merging / let me know if you have any comments.