Made TextArea and TextBox views compatable with disabled property

IPython/html/static/notebook/js/widgets/string.js

@@ -46,6 +46,9 require(["notebook/js/widget"], function(){
                 this.$textbox.val(this.model.get('value'));
             }
 
+            var disabled = this.model.get('disabled');
+            this.$textbox.prop('disabled', disabled);
+
             var description = this.model.get('description');
             if (description.length == 0) {
                 this.$label.hide();
@@ -96,6 +99,9 require(["notebook/js/widget"], function(){
                 this.$textbox.val(this.model.get('value'));
             }
 
+            var disabled = this.model.get('disabled');
+            this.$textbox.prop('disabled', disabled);
+
             var description = this.model.get('description');
             if (description.length == 0) {
                 this.$label.hide();