fix indefinite article

Mateusz Stebnicki · Mateusz Stebnicki · commit 064dd896c7eb · 2015-09-18T17:05:33.000+02:00
diff --git a/README.md b/README.md
@@ -404,7 +404,7 @@ Though this method is convenient you should strongly consider using `OAuth` for
 
 ### 3.2 Authorizations API
 
-#### 3.2.1 For an User
+#### 3.2.1 For a User
 
 To create an access token through the GitHub Authrizations API, you are required to pass your basic credentials and scopes you wish to have for the authentication token.
 
