Fixed z-index of search results dropdown #2626

Fixed the z-index of search results dropdown menu #2626.
Also fixed the inconsistent hover-state over the search results so that the text is white for all results.
![search dropdown menu](https://cloud.githubusercontent.com/assets/2066060/4946803/6764c018-6619-11e4-9879-df1b5b01395c.png)