Modifying 3D Correlation Function

I'm changing the 3D correlation function code to accept data and randoms (similar to what I just did for the 2D correlation function code).

This is proving to be a little tricky because in the current version I do some tricks to make sure the periodic boundary conditions don't add power incorrectly, and I also re-scale the data because the correlation function is expecting it to be in a 1X1X1 box.

After talking with Alexia, I've decided to do these conversions outside of the correlation function in python, such that the code expects the data to be in a 1x1x1 box.

Results to come soon.....