Prevented re-rendering crumb scenes
Prevented re-rendering crumb scenes

When shared elements came in, it brought in context. Turns out
ReactReconciler always re-renders when context is there. Before context
it the reconciler short circuited the update because the scenes where
=== identical. So, cached the url in constructor and added a
shouldComponentUpdate to avoid re-rendering crumb scenes

grahammendick/navigation,grahammendick/navigation,grahammendick/navigation,grahammendick/navigation,grahammendick/navigation,grahammendick/navigation,grahammendick/navigation