Issue #2803: fixed a bug for cc.Sprite that its drawing doesn't work when _rect's width or height greater than 0 and less than 1.
Issue #2802: update some information in CHANGELOG.txt
Merge pull request #1142 from dingpinglv/Iss2803_V2.1.6Release

Issue #2803: fixed a bug for cc.Sprite that its drawing doesn't work when _rect's width or height greater than 0 and less than 1.