Clean up from Pull request #2 (from Bitbucket code)

[sfield17]

Pull request #2 (bitbucket) was a bit of a rush job to get the code working. Three key pieces of cleanup work remain:

1. param nudging might be best suited for TensorSplineGrid class which is what actually needs nudging. It will make independent calls to this class easier too

2. consistent coding style.

3. remove memoize decorator (see Jonathan's email "fast spline" for how to do this correctly)