title: marker react native map can't drag
body: <p>i' ve using react-native-map air bnb to render a google map in my native app.
  The map and marker is showed up but the marker can't drag.
  this is my script</p>
  
  <pre><code>&lt;View style={Style.mapContainer}&gt;
              &lt;GeoLocation onSetInitalPos={this.onSetInitialPosition}
                           onSetLastPos={this.onSetLastPosition}/&gt;
              &lt;MapView style={Style.map} region={this.state.region} onRegionChange={this.onRegionChange}&gt;
                  &lt;MapView.Marker draggable={this.state.draggable}
                                  coordinate={this.state.marker.latlng}
                                  title={this.state.marker.title}
                                  description={this.state.marker.description}
                                  onDrag={() =&gt; console.log('onDrag')}
                  /&gt;
              &lt;/MapView&gt;
              &lt;AutoCompleteMap onSetNewPlace={this.setMarkerPosition}/&gt;
          &lt;/View&gt;
  </code></pre>