minor hot fix in screen registration, release 0.1.2

package.json

     "type": "git",
     "url": "https://github.com/wix/react-native-navigation.git"
   },
-  "version": "0.1.1",
+  "version": "0.1.2",
   "description": "React Native Navigation - truly native navigation for iOS and Android",
   "nativePackage": true,
   "bugs": {

src/Navigation.js

     };
   }
   registerScreen(screenID, generatorWrapper);
+  return generatorWrapper;
 }
 
 function _registerComponentRedux(screenID, generator, store, Provider) {
     };
   }
   registerScreen(screenID, generatorWrapper);
+  return generatorWrapper;
 }
 
 function getRegisteredScreen(screenID) {