1.7 Sky World Seed

It isn't as easy as most seeds.

Steps (windows):

1. If Minecraft is open, close it,
2. Open minecraft.jar
3. Download the wr.class file here.
4. Open minecraft
5. Create New World
6. In the seeds section, type:
As seen on his Twitter

Steps (Mac):
1. If Minecraft is open, close it,
2. Download MacModder
3. Open mod installer
4. When ConMods is open, download wr.class here
 5. Click continue
6. Create New World
7. In the Seeds section, type:
As seen on his Twitter

You got it! :D