Fix 'getImageUrl' function

[koppthe]

Fix the problem that can not extracts the correct url of image from compressed CSS rule.

If there is another brackets after background rule, the getImageUrl function can't extract the correct url of image.

Input:

.share-container .plane{width:75px;height:75px;background-image:url("../img/other/plane.png");background-repeat:no-repeat;-webkit-transform:scale(0.5);transform:scale(0.5);}

Output:

"../img/other/plane.png);background-repeat:no-repeat;-webkit-transform:scale(0.5);transform:scale(0.5"

Expect:

"../img/other/plane.png"