-[SPINE] Fixes Atlas attachment loader bug in which it would try to load the name of the attachment as a sprite instead of the name of the sprite.
-[STRIP] "padding" renamed to "canvasPadding" to reflect the fact that it is only used in canvas mode + canvas padding is calculated using the world transform to make sure it looks right at any scale.
-[SPINE] Spine loader uses a canvas padding of 1.5, optimal for most use cases.
Merge branch 'dev' of github.com:GoodBoyDigital/pixi.js into Trompo-SpineUpdate
Merge pull request #1233 from TrompoGames/Trompo-SpineUpdate

[SPINE] Spine fixes + strip canvas renderer improvements.