rename article filter plugins

plugins/af_gocomics/af_gocomics.php

@@ -1,5 +1,5 @@
 <?php
-class GoComics extends Plugin {
+class Af_GoComics extends Plugin {
 
 	private $link;
 	private $host;

plugins/af_pennyarcade/af_pennyarcade.php

@@ -1,5 +1,5 @@
 <?php
-class PennyArcade extends Plugin {
+class Af_PennyArcade extends Plugin {
 
 	private $link;
 	private $host;

plugins/af_redditimgur/af_redditimgur.php

@@ -1,5 +1,5 @@
 <?php
-class RedditImgur extends Plugin {
+class Af_RedditImgur extends Plugin {
 
 	private $link;
 	private $host;