update rn version to 0.57.3 for demo

demo/package.json

     "test": "jest"
   },
   "dependencies": {
-    "react": "16.5.0",
-    "react-native": "0.57.2",
-    "react-native-autoheight-webview": "../"
+    "@babel/core": "^7.1.2",
+    "react": "16.6.0-alpha.8af6728",
+    "react-native": "0.57.3"
   },
   "devDependencies": {
-    "babel-core": "7.0.0-bridge.0",
-    "babel-jest": "23.4.0",
-    "jest": "23.4.1",
-    "metro-react-native-babel-preset": "^0.45.0",
-    "react-test-renderer": "16.4.1"
+    "jest": "23.6.0",
+    "metro-react-native-babel-preset": "^0.48.1",
+    "react-test-renderer": "16.6.0-alpha.8af6728"
   },
   "jest": {
     "preset": "react-native"