Spike cocoon

Idea I had before S2, ha... Changed the dialogue a bit to reflect that, but mostly just rushed through this to get it out of my WIP folder (I've not seen "Spike will get wings after cocooning" before, so I figured it was worth finishing).

That he was meant to come out like an attractive-stallion-like-dragon didn't really come across very well, I think (poor anatomy is poor). Still, there are lots of "Spike as a pony" things out there so I'm sure it's covered.

Probably for Scraps soonish.