Use transitions instead of :hover (css)

[y21]

Describe the bug
The animations in the main menu are nice, but once your mouse leaves the button, the element will jump to its default rules.

To Reproduce
Steps to reproduce the behavior:

1. Login
2. Hover over any button that has animations
3. Leave it with your mouse

Expected behavior
It shouldn't immediately "jump" to its previous rules but have an animation.

Screenshots

[y21]

Fixed in fb9b73b. Animations are smoother now and fade out when the mouse leaves the button.