@ashfurrow => clean up divider lines in collection views

Instead of using a 1-px view for our dotted and solid borders/dividers, let's just use the ARDrawing methods we have in the UILabels pod to draw a border layer on whatever view requires a border.

We were sort of doing this in the place where we were supposed to be using a dotted border, but we were basically adding a dotted border to a 1px UIView that was already serving as a solid border. This gets rid of all those single pixel divider views.

The table views looks the same as before with this change:
![screen shot 2014-10-22 at 1 31 35 pm](https://cloud.githubusercontent.com/assets/3171662/4740913/afc431ea-5a11-11e4-9bef-9266a28b68c6.png)

And the dotted divider actually looks right now:
![screen shot 2014-10-22 at 1 31 47 pm](https://cloud.githubusercontent.com/assets/3171662/4740920/c66d7ffa-5a11-11e4-9958-f089227a1bfb.png)

this just seemed like a mistake. ListingsCollectionViewCell is the superclass of MasonryCollectionViewCell, so it seems weird for all of ListingsCollectionViewCell's subviews to be created by MasonryCollectionViewCell methods. Was there some reason for this?