Pages before the page "push" need not be drawn

[iwangx]

Version

Tell us which versions you are using:

• react-native-router-flux v4.0.0-beta.27
• react-native v0.51.0

Expected behaviour

Push three pages like Navigator and then look at the layout on the Xcode

I think the page before the current page should not be drawn out, so it will consume unnecessary memory, I hope to improve, thank you.

Actual behaviour

After using react-native-router-flux to push three pages, look at the layout on the Xcode

This will cause an increase in memory, which may cause app to crash.

[aksonov]

Please try to reproduce it with Example project and latest version 4.0.0-beta.40. Feel free to open if the issue still exists