Further corrections to plotting script
Add support for reading HDF5 snapshots
Cleanup HDF5 reading routines and move them to the file for reading
Generalise the power spectrum routine to allow computation of cross-correlations
Implement computing the cross-correlation of a species with the CDM
Fix bug by properly zeroing array in the HDF5 case
Fix double counting of first file in snapshot
Zero the cross corr field just to be safe
Fix daft mistake