Added excludeLastSingleItem option and functionality

[avjaarsveld]

Users can set excludeLastSingleItem (default false) to exclude the last item from the wrecker table if there is an odd number of items. This allows for the last item to appear as if it's in the last row of the table but spanning multiple columns (using CSS).

Example:
JS:
Container.wrecker({
itemSelector : ".single_entry",
maxColumns : 2,
excludeLastSingleItem : true
});

CSS:
.wrecker-single-last {
background-color: $table-bg-color;
border-top: $table-border;
//etc
}