Fixes #540. Remove deprecated way of initializing plugins.

Should already have been removed in the previous release.

converse.js

@@ -6347,9 +6347,6 @@
 
                 if (typeof plugin.initialize === "function") {
                     plugin.initialize.bind(plugin)(this);
-                } else {
-                    // This will be deprecated in 0.10
-                    plugin.bind(this)(this);
                 }
             }.bind(this));
         };

docs/CHANGES.md

@@ -5,6 +5,7 @@
 - #524 Added `auto_join_on_invite` parameter for automatically joining chatrooms. [ben]
 - #521 Not sending presence when connecting after disconnection. [jcbrand]
 - #536 Presence not sent out (in cases where it should) after page refresh. [jcbrand]
+- #540 `bind is not a function` error for plugins without `initialize` method. [jcbrand]
 - A chatroom invite might come from someone not in your roster list. [ben]
 
 ## 0.10.0 (2015-11-05)