Allowing to set tileLayers inside 'defaults' so that you can setup multiple layers for custom zoom levels.

I added support to allow this code to work:

    $scope.defaults = {
        layers: [
            L.tileLayer([here the tile url]), {
                maxZoom: 13,
                minZoom: 0,
            }),
            L.tileLayer('[here the tile url]', {
                minZoom: 14,
                maxZoom: 18
            })
        ]
    }