add method centerOrigin to Sprite and AtlasSprite
I am bad at words
Return the area width and not the area height for ScrollPane's getScrollWidth method.
rename method
Merge pull request #1500 from lioncash/scrollpane

Fix a possible typo in ScrollPane's getScrollWidth method.
Merge pull request #1492 from jrenner/sprite

add method centerOrigin to Sprite and AtlasSprite