Add a fourth part type 'neither' for the case when the top and bottom of the element are both offscreen.
Add a fourth part type 'neither' for the case when the top and bottom of the element are both offscreen.

talis/angular-inview,eugenehp/angular-inview,talis/angular-inview,mastertheblaster/angular-inview,thenikso/angular-inview,Nex9/angular-inview,Nex9/angular-inview,MartyIX/angular-inview,jgknott/angular-inview