Merge pull request #392 from Microsoft/update-react-gradle-location

Update react.gradle location in setup docs

Author: geof90

README.md

@@ -216,7 +216,7 @@ In order to accommodate as many developer preferences as possible, the CodePush
 
     ```gradle
     ...
-    apply from: "react.gradle"
+    apply from: "../../node_modules/react-native/react.gradle"
     apply from: "../../node_modules/react-native-code-push/android/codepush.gradle"
     ...
     ```