A bunch of Objective-C code snippets originally by Mattt Thompson, converted to .codesnippet for easy installation by Nicolas Bouilleaud
Just copy the snippets to ~/Library/Developer/Xcode/UserData/CodeSnippets/.
Alternatively, use the Install System Plugin tool and double-click the codesnippet files.
Or alternatively you could checkout the repo somewhere and run rake install from it's directory. It will create symbolic link from your checout into ~/Library/Developer/Xcode/UserData/CodeSnippets. For example I've added this repo as a submodule to my dotfiles repo.