Windspeed compass

This adds a windspeed compass to the map.

![screen shot 2013-05-28 at 5 18 04 pm](https://f.cloud.github.com/assets/1118185/573111/fdab1d0c-c7a9-11e2-9a9b-170abbf18896.png)

The compass can be turned off for those who prefer a cleaner look:
![screen shot 2013-05-28 at 5 18 27 pm](https://f.cloud.github.com/assets/1118185/573114/054601da-c7aa-11e2-9f05-37a33fb8a21d.png)
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![screen shot 2013-05-28 at 5 18 36 pm](https://f.cloud.github.com/assets/1118185/573115/069d2a40-c7aa-11e2-88e5-9b162ab311a0.png)