[BUGFIX] Add class.dmailsubscribe.php to classmap

This fixes autoloading in non-composer mode.

Closes: #4

ext_emconf.php

@@ -42,5 +42,10 @@
         'suggests' => array(
         ),
     ),
+    'autoload' => array(
+      'classmap' => array(
+        'pi/class.dmailsubscribe.php',
+      )
+    ),
     '_md5_values_when_last_written' => 'a:13:{s:9:"ChangeLog";s:4:"2578";s:12:"ext_icon.gif";s:4:"8d58";s:14:"ext_tables.php";s:4:"8517";s:14:"ext_tables.sql";s:4:"1e8e";s:15:"fe_adminLib.inc";s:4:"715e";s:13:"locallang.php";s:4:"1ab3";s:16:"locallang_db.xml";s:4:"f6d4";s:10:"README.txt";s:4:"e4af";s:27:"pi/class.dmailsubscribe.php";s:4:"44f7";s:30:"pi/fe_admin_dmailsubscrip.tmpl";s:4:"a4dd";s:16:"pi/locallang.xml";s:4:"c842";s:20:"static/constants.txt";s:4:"3daf";s:16:"static/setup.txt";s:4:"e9a2";}',
 );