Visual Cues improvements

[damianhxy]

• Does not correctly collapse to 2 columns on small screens
• Clearfix does not change depending on number of columns
• (Requested by 122) Display start and end date (and maybe more) as a mouse-over instead
• (Requested by Joey) show on course index page too

Quick and dirty prototype:

.collection-item .date {
  display: none;
}

.collection-item:hover .date {
  display: block;
}

Possibly add a small icon to draw user attention