Test ICO files with JPG names
Stubbornly load images if we see MissingDelegateError

For some reason, Wand doesn't try to load ICO files as they are
if you pass in a blob and you don't specify the format.  So if
we fail to load an image, we just try loading it as an ICO file.
Detecting the format via magic numbers or something would probably
be a better long term solution
Don't try loading the custom key if we're forcing

We're not going to use it anyway, so why load it in the first
place?
Test a large resize of an ICO file pretending to be a JPG

ICO files max out at 256x256, so this test just makes sure that
the transform happens after the format change
Merge pull request #21 from hoelzro/master

More tests, fixes, and performance enhancements