Thanks, looking for one of these for quite awhile now.
Your problem is that you registered your registry name wrong. To check what your actual name is, load Minecraft, open the command console and type in
/give <player> tm: and then hit Tab.
Hitting Tab will show you what your actual name in the game is. The line you need to change is:
GameRegistry.registerItem(Item i, String name)
Change the name to super_sword.