Add media queries when grouping selectors

[dmazinanian]

Right now, we group selectors that have the same media query, but we don't add the media query to the resulting grouping selectors.

(Code from BS)

@media (max-width :767px) {
	.visible-xs {
		display: block !important
	}
...
}

@media (max-width :767px) {
	.visible-xs-block {
		display: block !important
	}
}

Result:

.visible-xs, .visible-xs-block {
	display: block
}