Added support for party parrot.

[obicons]

Added support for using party parrot or nyan.

I added a cache to store animations + images so that they're only loaded once, as before. Only now, the animation/image is loaded based on the value of nyan-image. When nyan-image is 'nyan (the default), the Nyan is used. When nyan-image is 'parrot, party parrot is used.