Fix typo in sample output
Changed `ICONTAINER ID` to `CONTAINER ID`.
@@ -74,7 +74,7 @@ svendowideit/testimage version3 f5283438590d 16 sec
```bash
$ docker ps
-ICONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
+CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
c3f279d17e0a ubuntu:12.04 /bin/bash 7 days ago Up 25 hours desperate_dubinsky
197387f1b436 ubuntu:12.04 /bin/bash 7 days ago Up 25 hours focused_hamilton
