As of 0.2.0, custom markers no longer work in Marker.vue #92
Description
Prior to 0.2.0, creating the mapbox marker instance happened in the mounted hook via the old deferredMount concept. Now that it has been moved to the created hook in 0.2.0, the $slots.marker[0] VNode has not yet mounted; so, $slots.marker[0].elm is undefined.