Specifying height causes infinite loop

[jhogendorn]

line 309 to 329 loops indefinitely if you specify a height, rather than adding elements to the columns it continues to keep adding more and more last columns.

this breaks the horizontal scrolling capability.

using:
width: 400
height: 600
lastNeverTallest: true

[adamwulf]

this looks like the same bug as #47 - just fixed in master. thanks!