Use Homebrew'ed emacs as default on Mac OSX

$ brew update
$ brew install emacs --cocoa


 To link the application to a normal Mac OS X location:
   brew linkapps
 or:
   ln -s /usr/local/Cellar/emacs/24.3/Emacs.app /Applications



[Reference] http://wikemacs.org/index.php/Installing_Emacs_on_OS_X