Window listener optimization

[mbilotta]

Instead of always listening to window resize events, start/stop listening when ellipsis-resize-detection changes to/from window.

This change should improve performance when many instances of this directive are in use at the same time with detection strategies other than window.

[lentschi]

Thanks @mbilotta !
... and sorry that it took me so long to merge. It's now published as version 2.2.2.

At first, I thought there should be hardly any performance impact by the HostListener as it didn't run any code when not running with the window change detection strategy.
It turns out though, that whenever someone was resizing the window this caused ngAfterViewChecked to be run in every component of the app. (This is by angular's design.)

So, if there is a lot of code in the consuming app's ngAfterViewChecked methods, your change should really boost performance!