Namespace window resize event, so it may be elegantly unbound

[bsheldon]

With pages that require high performance, sometimes with many high-resolution images being rendered concurrently, it's important to be able to debounce the internal update call/check.

Currently this can be achieved for scrolling (or other rapid-fire events) by passing a custom trigger method to the plugin's event setting, and any debouncing magic could be handled (with your utility lib of choice) prior to triggering said event.

However, window resize cannot currently be debounced, as is. It's not possible to unbind the resize event that is directly set on the window without actually clobbering any other resize events also attached (perhaps by other libs).

For a simple fix, we can namespace the plugin resize event to allow for easy unbinding where necessary. For example, any window resize debouncing magic could be handled prior to calling the custom event.