Remove v-once from the GlMap element (#29)
Remove v-once from the GlMap element (#29)

Removing `v-once` from inside the GlMap element so it can be controlled by the user.  `v-once` can now be placed on the element when being used:

```html
<mgl-map
  v-once
  :accessToken=“accessToken”
  :mapStyle.sync="mapStyle"
></mgl-map>
```

This allows markers to be created and removed using `v-if`.
soal/vue-mapbox