hideTabBar nested tabs do not work

### Version
Tell us which versions you are using:
- react-native-router-flux v4.0.6
- react v16.4.1
- react-native v0.56.0

### Expected behaviour
`hideNavBar` prop should hide the most recent (one up) TabBar

### Actual behaviour
`hideNavBar` prop hides all TabBars

Additionally, if I have a nested Tab Scene and override `tabBarComponent={}`, both the outer TabBar and inner TabBar are replaced with TabBarComponent. The expected behavior should be that only the inner TabBar renders `tabBarComponent`.

### Steps to reproduce
1. Create a root Scene
2. Create a Tabs scene with prop `showTabs={true}`
3. Create a second Tabs scene nested within the first
4. Create two "Scene" inside the second Tabs (to show that the TabBars are different)
5. In one of the scenes, use prop `hideTabBar={true}`

### Reproducible Demo
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Thank you guys. For now I think I'll replace the inner Tab Scene with a normal scene, and use Actions.replace('two') instead of Actions.jump('two').