A better prelude-view-url

- remove HTTP headers, what we care most of the time is the content
- `set-auto-mode` is way better than the naive xml, html tag check

core/prelude-core.el

@@ -266,8 +266,11 @@ there's a region, all lines that region covers will be duplicated."
          (url (read-from-minibuffer "URL: " default)))
     (switch-to-buffer (url-retrieve-synchronously url))
     (rename-buffer url t)
-    (cond ((search-forward "<?xml" nil t) (nxml-mode))
-          ((search-forward "<html" nil t) (html-mode)))))
+    (goto-char (point-min))
+    (re-search-forward "^$")
+    (delete-region (point-min) (point))
+    (delete-blank-lines)
+    (set-auto-mode)))
 
 (defun prelude-cleanup-buffer-or-region ()
   "Cleanup a region if selected, otherwise the whole buffer."