Merge pull request #440 from danilospa/master

Add info on README for includeModules configuration

README.md

@@ -284,8 +284,8 @@ custom:
 
 
 All modules stated in `externals` will be excluded from bundled files. If an excluded module
-is stated as `dependencies` in `package.json`, it will be packed into the Serverless
-artifact under the `node_modules` directory.
+is stated as `dependencies` in `package.json` and it is used by the webpack chunk, it will be
+packed into the Serverless artifact under the `node_modules` directory.
 
 By default, the plugin will use the `package.json` file in working directory, If you want to
 use a different package file, set `packagePath` to your custom `package.json`: