Remove any and all references to numpy and scipy

The tests have been updated to use cached(files and values in test code) scipy and numpy results. By doing this, we remove the need to run numpy and scipy for the tests since we have the recorded values. Additionally, all dependency references to numpy and scipy have been removed along with the entire stats.cluster package.

Resolves: https://github.com/cbmi/avocado/issues/90 and https://github.com/cbmi/avocado/issues/89