fixed #1001 fixed a bug that LabelTTF dimension behavior doesn't support height=0
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-html5 into Iss1001_LabelTTFSupportHeight=0
Merge pull request #1002 from dingpinglv/Iss1001_LabelTTFSupportHeight=0

fixed #1001 fixed a bug that LabelTTF dimension behavior doesn't support height=0