Merge pull request #144 from jtwigg/develop

Lock audio preview to the top and resize properly.
Fixes constrains on file previews
Changes the minimum window size
Updates Cocos2d
Adds font size to CCTextField and support for content size types. Fixes #143
opacity now works as animatable property.
Merge branch 'develop' of https://github.com/apportable/SpriteBuilder into develop