Added authorization URL to the Apis

src/main/java/org/scribe/builder/api/DefaultApi10a.java

@@ -117,6 +117,15 @@ public abstract class DefaultApi10a implements Api
    */
   public abstract String getAccessTokenEndpoint();
   
+  /**
+   * Returns the URL where you should redirect your users to authenticate
+   * your application.
+   * 
+   * @param requestToken the request token you need to authorize
+   * @return the URL where you should redirect your users
+   */
+  public abstract String getAuthorizationUrl(Token requestToken);
+  
   /**
    * Returns the {@link OAuthService} for this Api
    *