We don't actually need a rails.png in the AP fixtures, the tests
that use it don't actually try to load the file.
We also don't need to get rid of it with the dummy reset either.
Finally, it's not needed in the sample application that's included
with the Rails Guides.
The sample application with the Getting Started Guide was very out of
date. I've re-done it on edge (as of 51b9def5bf) so it should
be good to go with Rails 4. It's also in synch with what the guide
actually says.
Nick