Can't set Title style

[毒枭东]

https://github.com/react-native-community/react-native-navbar/blob/master/index.js#L56

• the bug code

<Text style={[styles.navBarTitleText, colorStyle]}>
    {data.title}
</Text>

• should be

<Text style={[styles.navBarTitleText, data.style, colorStyle]}>
    {data.title}
</Text>