Fix edit buttons not triggering change events

The discussion in refactory-id#308 indicates that `this.change(this)` is incorrect, adding a listener instead of triggering a change event.

js/bootstrap-markdown.js

@@ -199,7 +199,7 @@
       callbackHandler(this);
 
       // Trigger onChange for each button handle
-      this.change(this);
+      this.$textarea.change();
 
       // Unless it was the save handler,
       // focusin the textarea