In case anyone missed it, Spine got a significant update yesterday, with better weight and mesh tools + clipping/ finally! Clipping not ideal for everything (using a vertices system) so complex masks may still need to be done manually. Still nice for quick and simple masks!
Just tested in PIXI and clipping not working as I imagined, but hopefully could be added to pixi-spine soon? 
http://esotericsoftware.com/blog