Minor README tweak

Author: jamonholmgren

.gitignore

@@ -36,6 +36,8 @@ lib/android/src/main/gen
 node_modules/
 npm-debug.log
 yarn-error.log
+package-lock.json
+yarn.lock
 
 # Rubygem bundles
 #

README.md

@@ -10,8 +10,10 @@
 
 ## Installation
 
+*Note: this is currently a work-in-progress and not yet published to NPM.*
+
 ```
-$ npm install --save react-native-webview
+$ npm install --save https://github.com/react-native-community/react-native-webview
 $ react-native link react-native-webview
 ```