Add Support for Animations

[jciskey]

While working to utilize the library, I noticed that it doesn't load animation data from scenes, or any way to do animation rendering beyond the sample provided for sprites in the advanced examples section.

Is this something on the feature map, open for PRs with implementation, or outside the intended scope of the library?

Assuming it's open for PRs, is a minimum basic implementation acceptable for the first iteration? I'm thinking primarily in terms of GLTF scenes and their animation data.

[einarf]

Definitely open for PRs. Getting something basic like translation/rotations of nodes is a good start I guess. For mesh animations this data is at least prepared already.

The current screne structure was done in a great hurry to get things started. It's fairly simple and can be tweaked. Probably also a good idea to throw out pyrr for pyglm.