Fixed 'seven-stairs' and 'room-warzone'

Removed the trees in room-warzone
![roomwarzonebug](https://cloud.githubusercontent.com/assets/7704140/3752626/051046e2-180a-11e4-91ca-4ff056d93dd0.png)
and added a missing tile in seven stairs.
![sevenstairsbug](https://cloud.githubusercontent.com/assets/7704140/3752661/5ada3a24-180a-11e4-9379-1114ea685faf.png)
Looks now so
![roomwarzonefixed](https://cloud.githubusercontent.com/assets/7704140/3752726/f71a8ede-180a-11e4-8bb8-63d6c91a0d7e.png)
and so.
![sevenstairsfixed](https://cloud.githubusercontent.com/assets/7704140/3752725/f69b899a-180a-11e4-9f64-fb0f4ba6ac61.png)