Make submenu show/hide through DISPLAY and not VISIBILITY


![cats](https://cloud.githubusercontent.com/assets/5834903/3282183/1965704a-f4dd-11e3-9c0b-4f76d089fac7.jpg)
I ran into an issue where if I used CSS3 transition duration on the menu links, it would create a submenu lagging effect where they would be slow to disappear and could overlap one another.