Bugfix for issue Tree case-sensitivity with rename #136.
NSFileManager's moveItemAtPath:toPath:error: will consider renaming foo.txt -> Foo.txt invalid since the file already exists. Fix renames in two steps: old -> tmp -> new.
Merge pull request #293 from NickyWeber/bugfix/issue_136

Bugfix for issue Tree case-sensitivity with rename #136.
publisher: extracted spritesheet generation into its own method
Updates the link to the SpriteBuilder-SK submodule
Fixes project file for default projects
SK texture atlas generation script
Merge branch 'develop' of github.com:apportable/SpriteBuilder into develop-steffen
publish Sprite Kit texture atlas