Fix navigation card stack pan responder

Summary:
Hi folks !
🔧 Fix the navigation card stack pan responder when the `vertical` direction is enabled.

**Issue:**
When using a `ScrollView` with the `vertical` direction enabled, the pan handler catch the gesture before the `ScrollView`.

I don't know why there was no default value here for `RESPOND_POSITION_MAX_VERTICAL` 5162eb3254
ericvicenti could you tell me what you think about setting a default value for `RESPOND_POSITION_MAX_VERTICAL` ? 😃

Thanks !!

**EDIT June 15, 2016**
I'll update this PR this week end to provide a way to give custom values as there is no magic value for `RESPOND_POSITION_MAX_VERTICAL`

**EDIT June 24, 2016**
I've added a props `gestureResponseDistance` to control both the `RESPOND_POSITION_MAX_VERTICAL` and `RESPOND_POSITION_MAX_HORIZONTAL`
Closes https://github.com/facebook/react-native/pull/8076

Differential Revision: D3605973

Pulled By: ericvicenti

fbshipit-source-id: 158d88cf8ebbab742bf0b38c217ae502e9dd1963

Libraries/CustomComponents/NavigationExperimental/NavigationCardStack.js

@@ -64,6 +64,7 @@ type Props = {
   renderScene: NavigationSceneRenderer,
   cardStyle?: any,
   style: any,
+  gestureResponseDistance?: ?number,
 };
 
 type DefaultProps = {
@@ -95,6 +96,7 @@ class NavigationCardStack extends React.Component<DefaultProps, Props, void> {
     renderOverlay: PropTypes.func,
     renderScene: PropTypes.func.isRequired,
     cardStyle: View.propTypes.style,
+    gestureResponseDistance: PropTypes.number,
   };
 
   static defaultProps: DefaultProps = {
@@ -164,6 +166,7 @@ class NavigationCardStack extends React.Component<DefaultProps, Props, void> {
     const panHandlersProps = {
       ...props,
       onNavigateBack: this.props.onNavigateBack,
+      gestureResponseDistance: this.props.gestureResponseDistance,
     };
     const panHandlers = isVertical ?
       NavigationCardStackPanResponder.forVertical(panHandlersProps) :