openlayers/ol3 — pull request #2847 by elemoine (2014-10-16 17:45:14+00:00)
Title: Constrain center in zoomify example

This is in response to a [question](https://groups.google.com/d/msg/ol3-dev/DuL6RlfpzoA/XqUriBhntLYJ) on the mailing list, and because it makes sense to constrain the center to an extent in that example.