title: make dynamic tab on createMaterialTopTabNavigator of react-navigation
body: <p>I'm making the top tab navigator using createMaterialTopTabNavigator of react-navigation. The problem I faced is that <strong>the tabs have to decide by the response data of API request.</strong> For example, I call an API to request the football team list, receive the list and then set the tabs of the <code>MaterialTopTabNvigator</code>. </p>
  
  <p>I already make the label of the navigator using the component like following :</p>
  
  <pre class="lang-js prettyprint-override"><code>class TabBarLabel extends React.Component {
    constructor(props) {
      super(props);
    }
    render() {
      return this.props.focused ? (
        &lt;View style={lstyles.container_focused}&gt;
          &lt;Text style={lstyles.label_focused}&gt;{this.props.name}&lt;/Text&gt;
        &lt;/View&gt;
      ) : (
        &lt;View style={lstyles.container_blur}&gt;
          &lt;Text style={lstyles.label_blur}&gt;{this.props.name}&lt;/Text&gt;
        &lt;/View&gt;
      );
    }
  }
  
  const FootballTeamNavigator = createMaterialTopTabNavigator(
    {
      teamA : {
        screen: AScreenComponent,
        navigationOptions: () =&gt; {
          return {
            title: 'teamA',
            tabBarLabel({focused}) {
              return &lt;TabBarLabel focused={focused} name="teamA" /&gt;;
            }
          };
        }
      }
    },
    {
      initialRouteName: teamA,
      swipeEnabled: false,
      timingConfig: {
        duration: 1000,
      },
      tabBarOptions: {
        scrollEnabled: true,
        ...styles,
      },
    },
  );
  </code></pre>
  
  <p>What I want to do is like :</p>
  
  <pre class="lang-js prettyprint-override"><code>let teamList = {};
  
  apiForGetFootballTeamList().then(response =&gt; {
    for (const team of response.data.list) {
      tempList[team.name] = team;
    }
  });
  
  createMaterialTopTabNavigator(
    {
      ...teamList
    },
    {
      initialRouteName: ...,
      ...
    }
  );
  </code></pre>
  
  <p>But I don't know how can I update the tabs using data, like component. (component has state and if we update the state, the component is updated)</p>
  
  <p>Is there any way for it?</p>