context: delegate etag/last-modified

lib/context.js

@@ -139,10 +139,10 @@ delegate(proto, 'response')
   .access('body')
   .access('length')
   .access('type')
+  .access('lastModified')
+  .access('etag')
   .getter('headerSent')
-  .getter('writable')
+  .getter('writable');
-  .setter('lastModified')
-  .setter('etag');
 
 /**
  * Request delegation.

lib/response.js

@@ -321,6 +321,17 @@ module.exports = {
     this.set('ETag', val);
   },
 
+  /**
+   * Get the ETag of a response.
+   *
+   * @return {String}
+   * @api public
+   */
+
+  get etag() {
+    return this.get('ETag');
+  },
+
   /**
    * Return the request mime type void of
    * parameters such as "charset".