navigator.getCurrentRoutes()

Summary:
According to our talk with @ericvicenti about `renderScene` arguments
Closes #553
Github Author: Kureev Alexey <kureev-mail@ya.ru>

Test Plan: Imported from GitHub, without a `Test Plan:` line.

Author: Kureev Alexey

Libraries/CustomComponents/Navigator/Navigator.js

@@ -318,6 +318,7 @@ var Navigator = React.createClass({
       popToRoute: this.popToRoute,
       popToTop: this.popToTop,
       parentNavigator: this.props.navigator,
+      getCurrentRoutes: this.getCurrentRoutes,
       // We want to bubble focused routes to the top navigation stack. If we
       // are a child navigator, this allows us to call props.navigator.on*Focus
       // of the topmost Navigator
@@ -998,6 +999,10 @@ var Navigator = React.createClass({
     }
   },
 
+  getCurrentRoutes: function() {
+    return this.state.routeStack;
+  },
+
   _onItemRef: function(itemId, ref) {
     this._itemRefs[itemId] = ref;
     var itemIndex = this.state.idStack.indexOf(itemId);