Show titles in the nodes in a zoom in a specific level

#97
![screen shot 2013-12-29 at 2 42 21 pm](https://f.cloud.github.com/assets/2622152/1819357/d20bfec4-7086-11e3-87ad-845e2cab42b1.png)
![screen shot 2013-12-29 at 2 42 28 pm](https://f.cloud.github.com/assets/2622152/1819358/d20cd718-7086-11e3-815d-d6d93767a29a.png)