Update getting_started.rst

Fix typo "it's" in first paragraph should be "is".

Author: lockhart

docs/rest-framework/getting_started.rst

@@ -2,7 +2,7 @@ Getting started
 ===============
 
 Django OAuth Toolkit provide a support layer for `Django REST Framework <http://django-rest-framework.org/>`_.
-This tutorial it's based on the Django REST Framework example and shows you how to easily integrate with it.
+This tutorial is based on the Django REST Framework example and shows you how to easily integrate with it.
 
 Step 1: Minimal setup
 ---------------------