v0.10.0-dev5

• Added: length property to PageStack to find out how many pages the stack will generate.

• Added: PageStackNavigator.builder constructor for advanced scenarios to filter which pages are shown in the navigator.

• Fixed: an issue with getting RouteData.of(context) in some advanced circumstances.

• Breaking change: renamed and refactored some core Routemaster objects. Unlikely to affect anyone unless you're making custom stateful pages.