Hey now it's longer and harder to follow!

- can now spit out a JSON array of thumb & image
- doesn't die when -x and -y differ
- sorta correctly documents effect of -x and -y

This is to enable changes over on p1k3.com where I'm using a JSON list of
images to generate the random header image.  I wanted this because I'm
not using Flickr on the site any more, because fuck Verizon (who, in case
you had missed this iteration of the dismal tide, just bought the corpse
of Yahoo!).