locked react navigation version

Author: shubhnik

package.json

@@ -9,7 +9,7 @@
   "dependencies": {
     "react": "16.0.0-beta.5",
     "react-native": "0.49.3",
-    "react-navigation": "^1.0.0-beta.15",
+    "react-navigation": "1.0.0-beta.15",
     "react-redux": "^5.0.6",
     "redux": "^3.7.2"
   },