Update style.css

Update style.css

[The overflow property specifies what happens if content overflows an element's box. If overflow is clipped, a scroll-bar should be added to see the rest of the content.](http://www.w3schools.com/cssref/pr_pos_overflow.asp)

Affected [page](http://i3wm.org/docs/user-contributed/workspace-current-output.html), there could be more but I gave this one as example when the overflow is not set to auto.