fixed stage.hide() bug, created new isVisible() method, and moved visible check to container

src/Node.js

@@ -174,6 +174,12 @@ Kinetic.Node.prototype = {
             }
         }
     },
+    /**
+     * determine if shape is visible or not
+     */
+    isVisible: function() {
+        return this.attrs.visible;
+    },
     /**
      * show node
      */