[WIP] Zoom Controls

* Sets up custom zoom in/zoom out controls for map

#### Screenshots

##### Safari
![screen shot 2013-09-26 at 6 52 18 pm](https://f.cloud.github.com/assets/770277/1222645/9b724f7a-26fe-11e3-8422-169e73855289.png)

##### Chrome
![screen shot 2013-09-26 at 6 51 35 pm](https://f.cloud.github.com/assets/770277/1222650/a3e18450-26fe-11e3-8c23-22f55437252e.png)

##### Firefox
![screen shot 2013-09-26 at 6 55 04 pm](https://f.cloud.github.com/assets/770277/1222657/b808798e-26fe-11e3-98f5-c13c6c8e825a.png)