Optimised, autocropped asteroids

Okay, here is a pull request for the asteroids again but this time they are cropped and optimised (saved 19K), I created a new branch with the new files and deleted the old one to save on commits... but I still have a problem with these merges - how do I get rid of them? I've looked at rebase but it doesn't seem to list the merges as commits I can remove... my apologies...