better info icon on gray maps

Solves problem where info icon is illegible on gray maps.

Old:
![screen shot 2013-12-12 at 5 31 01 pm](https://f.cloud.github.com/assets/108094/1738028/23125ad2-637d-11e3-9206-16ed2b15d5f7.png)
![screen shot 2013-12-12 at 5 36 07 pm](https://f.cloud.github.com/assets/108094/1738073/eddb44a4-637d-11e3-808d-d143bb7bc3fe.png)

New:
![screen shot 2013-12-12 at 5 34 35 pm](https://f.cloud.github.com/assets/108094/1738054/a144c278-637d-11e3-853d-3318574100a2.png)
![screen shot 2013-12-12 at 5 36 31 pm](https://f.cloud.github.com/assets/108094/1738069/e3d7adbc-637d-11e3-8711-8b9a0a4b2f34.png)