Support for map event broadcasting

## Overview

**Map events for all!!**

:tada: 

This pull request adds support for all [Leaflet Map Events](http://leafletjs.com/reference.html#map-events) which are broadcasted on `rootScope`.

## Setting up listeners

Event listeners follow the similar naming convention as marker events with the format `leafletDirectiveMap.<leaflet event name>`.

### Example

    $scope.$on('leafletDirectiveMap.click', function(e, args) {
        // Args includes the original leaflet event
    });