Fixed Raster.reduce for non Image types #672
Fix for #595, handles the reduction of the x-axis for the Raster class itself correctly. The reduce method is currently shared between all Raster and Image classes and it only handled the Image case correctly. In future when we have integrated Raster types with the grid interfaces this should be refactored but it works fine for now.
It might be worth mentioning this in a comment as a reminder.
Otherwise looks fine, the pr build is passing and I'm happy to merge.