Remove duplicates from the doc's search

Hello,

This PR removes the duplicates from the doc's search input.

**Previously:**
![screen shot 2014-09-04 at 16 15 25](https://cloud.githubusercontent.com/assets/1178099/4150462/f7be64a6-343d-11e4-828a-f7053acd9ec0.png)

**After this commit:**
![screen shot 2014-09-04 at 16 14 55](https://cloud.githubusercontent.com/assets/1178099/4150472/012d040c-343e-11e4-9e59-ab16ededa4a7.png)

I hope it doesn't break anything :D

Thanks