find hands by id rather than index
fix getting finger by id
build previous commit
added return
build
fix same bug for tools, pointables, fingers
added handId to pointable object, checks to make sure hand exists.
cleaner diff
Fix getting frame farther back than the current this.history.idx

-1 % 60 === -1, so this would return this.history[-1] if you get the
previous frame when the current frame is at index 0.
Merge pull request #3 from sakabako/master

Fix getting pointables and hands by id, put handId on pointables