Updating the animated surface for RN 0.33

This commit https://github.com/facebook/react-native/commit/eb3360b02ab82d20bc3c3f38f543b0d742598346 requires this change.

src/index.js

@@ -55,7 +55,7 @@ module.exports = {
   AnimatedSurface: makeSurface({
     View: Animated.View,
     GLCanvas: Animated.createAnimatedComponent(GLCanvas),
-    getGLCanvas: glSurface => glSurface.refs.canvas.refs.node,
+    getGLCanvas: glSurface => glSurface.refs.canvas.refs._component,
     dimensionInvariant: (value, field) =>
       invariant(
         isAnimated(value) || typeof value === "number" && value > 0,