Added support for multiple Skin2D components.
In this implementation Skin2D objects go outside of normal bone structure but
under skeleton. In this you have to select bones that will modify skinned mesh.
Normal structure:
skeleton
  bones
    hip
      torso
  skinnedMeshes
    skin1 (Skin2D)
    skin2 (Skin2D)
Merge branch 'unstable' of https://github.com/Banbury/UnitySpritesAndBones into unstable

Conflicts:
	Assets/SpritesAndBones/Scripts/Skin2D.cs
Moved calculating weights to skeleton. Now SkinnedMeshes can be in skeleton structure.
Allow all bones to weights, not just deform bones.
Reverted using to using bone index so that vertex weights is show right.
Also deform works again.
Revert "Reverted using to using bone index so that vertex weights is show right."

This reverts commit 93b058d98fae51d973b67f1f8d5f6f069a95c1b4.
Merge pull request #1 from denvil/unstable

Unstable