React-native-router-flux: Tab bar not showing on Android

[vzhen]

Version

Tell us which versions you are using:

• react-native-router-flux v3.37.0
• react-native v0.38

Expected behaviour

Show tabbar

Actual behaviour

No tabbar on android emulator

Steps to reproduce

Tried this
```

and this

```

[vzhen]

Got it, we need icon={TabIcon}

[turbobuilt]

For anybody else who comes afterwards, here's how TabIcon is defined in the demo:

class TabIcon extends React.Component {
    render(){
        return (
            <Text style={{color: this.props.selected ? 'red' :'black'}}>{this.props.title}</Text>
        );
    }
}