hide-show-important

Heya Eduardo, by not having \!important on the classes, it's causing problems on any element that has a rule setting display to anything else but hidden. Bootstrap 3 made this change for the same reason, so I'm proposing we do it to fix some bugs in Liferay. We can do this here, but I don't know if you prefer it to be in the utilities-alloy.scss file. Let me know what you think. Thanks\!