Added more robust isContentEditable function
Added more robust isContentEditable function

Applies for all cases in which an element can be editable. For #820

rjgotten/canjs,shiftplanning/canjs,rasjani/canjs,rasjani/canjs,Psykoral/canjs,bitovi/canjs,whitecolor/canjs,gsmeets/canjs,patrick-steele-idem/canjs,rjgotten/canjs,beno/canjs,ackl/canjs,dispatchrabbi/canjs,rasjani/canjs,Psykoral/canjs,UXsree/canjs,bitovi/canjs,patrick-steele-idem/canjs,gsmeets/canjs,asavoy/canjs,dispatchrabbi/canjs,shiftplanning/canjs,asavoy/canjs,rjgotten/canjs,gsmeets/canjs,patrick-steele-idem/canjs,UXsree/canjs,bitovi/canjs,beno/canjs,ackl/canjs,Psykoral/canjs,whitecolor/canjs,beno/canjs,bitovi/canjs,Psykoral/canjs,rjgotten/canjs,whitecolor/canjs,rasjani/canjs,ackl/canjs,tracer99/canjs,tracer99/canjs,tracer99/canjs