Merge pull request #2239 from dingpinglv/develop

Sets mobile browser's default target-densitydpi to high-dpi
Issue #5920: Event binding methods are not uniform
Merge pull request #2240 from VisualSJ/3.0-3

Issue #5920: Event binding methods are not uniform
Adds setTargetDensityDPI/getTargetDensityDPI to cc.view.
Merge branch 'develop' of git://github.com/cocos2d/cocos2d-html5 into develop