docs(onBundle): clarify onBundle (#30)

Author: baerrach

README.md

@@ -133,14 +133,15 @@ browserify({
 
 ### onBundle
 
-A function that is called with the [browserify bundle](https://github.com/browserify/browserify#browserifyfiles--opts). This allows you to specify external files and plugins. See the [browserify docs](https://github.com/browserify/browserify#baddfile-opts) for methods available.
+A function that is called with the [browserify instance](https://github.com/browserify/browserify#browserifyfiles--opts). This allows you to specify external files and plugins. See the [browserify docs](https://github.com/browserify/browserify#baddfile-opts) for methods available.
 
 ```javascript
 // example
 browserify({
   onBundle (bundle) {
     bundle.external('react')
     bundle.plugin('some-plugin')
+    bundle.ignore('pg-native')
   }
 })
 ```