Container Height with a Stamp and columnWidth

Hi,

When you set a `columnWidth` for the `masonry` option of isotope, and use stamp, the layout method does not calculate the height as it should with a stamp.

In other words: if you have a stamp, and you've set a `columnWidth`, so; When there are no items in the grid, and you try to relayout everything, the container will set its height to 0 without considering the stamp.

Demo: http://codepen.io/anon/pen/gmXPyE
In the demo, click on **remove all** and then on **layout** and see the problem.

Is it a bug? becuase it hurts the performance and user experience in my website.

thanks!

Start with the linked CodePen demo and reproduce the sequence of removing all items, then triggering layout, with masonry columnWidth and a stamp configured. Trace the masonry layout behavior involved in that sequence; done means the container height still accounts for the stamp when no grid items remain.

Written by the indexing model from the issue text.