Added support for carouselTap message to be emitted when slide clicked/tapped

[scm6079]

This commit adds support for a carouselTap message to be emitted when the carousel has an item tapped (as opposed to dragged) - which allows parents to create controls that perform actions on tap (e.g. opening a full-screen viewer).

Within parent scopes (controller/directive/etc) you can:

     $scope.$on('carouselTap', function(event, target){
        console.log('YOU TAPPED!  The item you tapped is:', target );
     });

Those can use the target passed to determine an appropriate action as necessary.

[revolunet]

thanks Scott, can you please also add the information in the README ?