Add swipeable utility right buttons to tabel cell.
1. add SWTableViewCell files from git@github.com:CEWendel/SWTableViewCell.git.
2. let DZFeedItemCell extend SWTableViewCell instead of UITableViewCell.
3. let DZFeedViewContoller implement SWTableViewCellDelegate protocol as well.
4. add right buttons to each cell when created.
5. manually trigger the segue when cell is selected.