testing-feat support

Hi, 

I just added a [testing-feat] (http://hackage.haskell.org/package/testing-feat-0.4) [provider](http://hackage.haskell.org/package/test-framework-testing-feat-0.1.0.1) for test framework, and wanted to also have a support for properties here. 

I made the necessary changes to support testing-feat and I cleaned up the code a little bit, hopefully to your liking. 

If you disagree with any of the changes I made I'll happily roll them back.

Best,
Jonathan