Extract StepUi#detach

You can't see where this is going, because there is other code that is not
yet part of Liza.  ...sorry.

src/ui/step/StepUi.js

@@ -271,22 +271,6 @@ module.exports = Class( 'StepUi' )
     },
 
 
-    /**
-     * Detaches the step from the DOM
-     *
-     * @return StepUi self to allow for method chaining
-     */
-    detach: function()
-    {
-        if ( this.$content instanceof jQuery )
-        {
-            this.$content.detach();
-        }
-
-        return this;
-    },
-
-
     /**
      * Will mark the step as dirty when the content is changed and update
      * the staging bucket