Update README.md

Added description how to Protect your API with OAuth when using Grape
after PR 567.

#567 (comment)

README.md

@@ -6,8 +6,7 @@
 [![Gem Version](https://badge.fury.io/rb/doorkeeper.svg)](https://rubygems.org/gems/doorkeeper)
 
 Doorkeeper is a gem that makes it easy to introduce OAuth 2 provider
-functionality to your Rails application. As of [PR 567] it plays nicely with
-Grape framework.
+functionality to your Rails or Grape application.
 
 [PR 567]: https://github.com/doorkeeper-gem/doorkeeper/pull/567
 
@@ -30,6 +29,7 @@ https://github.com/doorkeeper-gem/doorkeeper/releases.
     - [Routes](#routes)
     - [Authenticating](#authenticating)
 - [Protecting resources with OAuth (a.k.a your API endpoint)](#protecting-resources-with-oauth-aka-your-api-endpoint)
+    - [Protect your API with OAuth when using Grape](#protect-your-api-with-oauth-when-using-grape)
     - [Route Constraints and other integrations](#route-constraints-and-other-integrations)
     - [Access Token Scopes](#access-token-scopes)
     - [Authenticated resource owner](#authenticated-resource-owner)
@@ -174,6 +174,36 @@ end
 You can pass any option `before_action` accepts, such as `if`, `only`,
 `except`, and others.
 
+### Protect your API with OAuth when using Grape
+
+As of [PR 567] doorkeeper has helpers for Grape. One of them is
+`doorkeeper_authorize!` and can be used in a similar way as an example above.
+Note that you have to use `require 'doorkeeper/grape/helpers'` and
+`helpers Doorkeeper::Grape::Helpers`.
+
+For more information about integration with Grape see the [Wiki].
+
+[PR 567]: https://github.com/doorkeeper-gem/doorkeeper/pull/567
+[Wiki]: https://github.com/doorkeeper-gem/doorkeeper/wiki/Grape-Integration
+
+``` ruby
+require 'doorkeeper/grape/helpers'
+
+module API
+  module V1
+    class Users < Grape::API
+      helpers Doorkeeper::Grape::Helpers
+
+      before do
+        doorkeeper_authorize!
+      end
+
+      # ...
+    end
+  end
+end
+```
+
 
 ### Route Constraints and other integrations