Prevent column drift by fixing the iframe and column widths to even integers.
Fixed a flaw in recalculateDimensions() where some resize events were dropped.

This has resulted in a small API change -- recalculateDimensions no longer
takes arguments. If you need a callback, you should listen for
'monocle:recalculated' and deafen() when it fires.
Always apply column width, even if rules are unchanged.

This solves a problem where page numbers could be out of whack
after changing the font scale in Formatting.