add gitignore
closed #3017: Fixed a bug of Scale9Sprite that it error when _scale9Image is null.
closed #3016: Fixed a bug of LayerGradient that it displays wrong when set content size.
Merge pull request #1200 from xingsenma/CCScale9Sprite#3017

closed #3017: Fixed a bug of Scale9Sprite that it error when _scale9Image is null.
Merge pull request #1201 from xingsenma/LayerGradient#3016

closed #3016: Fixed a bug of LayerGradient that it displays wrong when set content size.
Merge pull request #1199 from HoGarfield/Modify-CCFileUtils

It should listen to the method "onload" when not using IE browser
Merge pull request #1181 from rablwupei/add_gitignore

add gitignore
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-html5 into dirty_develop