Added pop animation to squares

Response to issue https://github.com/ritstudentgovernment/petitions/issues/10 
As a quick fix, since the flashing seems to occur during DOM manipulation while all new squares are being added, giving the squares a pop-in animation as an entrance makes it less uncomfortable to the
eyes when scrolling down.
If the pop-in animation is too much, a regular fade-in css3 keyframe animation can easily be made as well to transition the newer squares into view.