update readme with new functionality

Author: davidlumley

README.md

@@ -18,6 +18,33 @@ Or install it yourself as:
 
 ## Usage
 
+### OAuth Authentication
+
+If you've already got an OAuth access token, feel free to skip to API Client Setup.
+
+The MYOB API uses 3 legged OAuth2. If you don't want to roll your own, or use the [OmniAuth strategy](https://github.com/davidlumley/omniauth-myob) you can authenticate using the `get_access_code_url` and `get_access_token` methods that [ghiculescu](https://github.com/ghiculescu) has provided like so:
+
+  class MYOBSessionController  
+    def new
+      redirect_to myob_client.get_access_code_url
+    end
+
+    def create
+      @token         = myob_client.get_access_token(params[:code])
+      @company_files = myob_client.company_file.all
+      # then show the user a view where they can log in to their company file
+    end
+
+    def myob_client
+      @api_client = Myob::Api::Client.new({
+        :consumer => {
+          :key    => YOUR_CONSUMER_KEY,
+          :secret => YOUR_CONSUMER_SECRET,
+        },
+      })
+    end
+  end
+
 ### API Client Setup
 
 Create an api_client:
@@ -87,6 +114,12 @@ Return a list of all customers (a subset of contacts)
 
     api_client.customer.all
 
+#### Employees
+
+Return a list of all customers (a subset of contacts)
+
+    api_client.employee.all
+
 
 ## Todo