Switch to using xatlas-python

[expenses]

Someone write some nice python bindings for xatlas: https://github.com/mworchel/xatlas-python and I think it'd be a lot less hacky to use them as opposed to the current method of bundling a binary. I already did some digging into how the package can be used in Blender (mworchel/xatlas-python#11) and I came up with a basic script that works well: https://gist.github.com/expenses/08fd15539606fa97b8d50d3edf172a1b#file-blender_xatlas-py-L13. For my uses, it's already better than what this addon offers because it doesn't require any triangulation of meshes.

[mattedicksoncom]

Thanks, I'll give it a shot. It would hopefully make things more robust, as the triangulation order and triangulation in general seem to be issues that come up a lot.