added support for closeAllModals

example/src/screens/ModalScreen.js

           <Text style={styles.button}>Close Modal</Text>
         </TouchableOpacity>
 
+        <TouchableOpacity onPress={ this.onCloseAllPress.bind(this) }>
+          <Text style={styles.button}>Close All Modals</Text>
+        </TouchableOpacity>
+
       </View>
     );
   }
   onClosePress() {
     this.props.navigator.dismissModal();
   }
+  onCloseAllPress() {
+    this.props.navigator.dismissAllModals();
+  }
 }
 
 const styles = StyleSheet.create({

src/Navigation.js

   return platformSpecific.dismissModal(params);
 }
 
+function dismissAllModals(params = {}) {
+  return platformSpecific.dismissAllModals(params);
+}
+
 function showLightBox(params = {}) {
   return platformSpecific.showLightBox(params);
 }
   registerComponent,
   showModal,
   dismissModal,
+  dismissAllModals,
   showLightBox,
   dismissLightBox,
   startTabBasedApp: platformSpecific.startTabBasedApp,

src/Screen.js

   dismissModal(params = {}) {
     return Navigation.dismissModal(params);
   }
+  dismissAllModals(params = {}) {
+    return Navigation.dismissAllModals(params);
+  }
   showLightBox(params = {}) {
     return Navigation.showLightBox(params);
   }

src/platformSpecific.ios.js

     }
   });
   ControllerRegistry.registerController(controllerID, () => Controller);
-  ControllerRegistry.setRootController(controllerID, params.animationType, params.passProps || {});
+  ControllerRegistry.setRootController(controllerID);
 }
 
 function startSingleScreenApp(params) {
     }
   });
   ControllerRegistry.registerController(controllerID, () => Controller);
-  ControllerRegistry.setRootController(controllerID, params.animationType, params.passProps || {});
+  ControllerRegistry.setRootController(controllerID);
 }
 
 function _mergeScreenSpecificSettings(screenID, screenInstanceID, params) {
   Modal.dismissController(params.animationType);
 }
 
+function dismissAllModals(params) {
+  Modal.dismissAllControllers(params.animationType);
+}
+
 function showLightBox(params) {
   if (!params.screen) {
     console.error('showLightBox(params): params.screen is required');
   navigatorResetTo,
   showModal,
   dismissModal,
+  dismissAllModals,
   showLightBox,
   dismissLightBox,
   navigatorSetButtons,