add Context#hasContent

docs/api.md

@@ -192,6 +192,10 @@ app.context({
   if you have a typo an error will be thrown, displaying this list
   so you can make a correction.
 
+### ctx.hasContent
+
+  When the response status is __204__ or __304__ this returns __false__.
+
 ### ctx.length
 
   Return request Content-Length as a number when present, or undefined.

lib/context.js

@@ -71,13 +71,26 @@ module.exports = {
       val = n;
     }
 
-    if (204 == val || 304 == val) {
+    this.res.statusCode = val;
+
+    if (!this.hasContent) {
       this.res.removeHeader('Content-Type');
       this.res.removeHeader('Content-Length');
       this.res.removeHeader('Transfer-Encoding');
     }
+  },
 
-    this.res.statusCode = val;
+  /**
+   * Check if the response has content,
+   * aka is not a 204 or 304 response.
+   *
+   * @return {Boolean}
+   * @api public
+   */
+
+  get hasContent() {
+    var s = this.status;
+    return 204 != s && 304 != s;
   },
 
   /**