Added animated GIF

This is probably more useful as a proof of concept, but I added an animated GIF. If you have the source images for small_mult.png, you can probably do a much better job of making sure it's aligned, but for now I've made this and posted [it to Tumblr](http://notes.husk.org/post/46384359354/iss-location-maps-animated), so I thought I'd let you know.