Try replacing the lines you posted with these:
(add-to-list 'load-path "~/.emacs.d/") ;;; Markdown mode (autoload 'gfm-mode "markdown-mode.el" "Major mode for editing Markdown files" t) (setq auto-mode-alist (cons '("\\.text$" . gfm-mode) auto-mode-alist)) (setq auto-mode-alist (cons '("\\.md$" . gfm-mode) auto-mode-alist)) (setq auto-mode-alist (cons '("\\.mdown$" . gfm-mode) auto-mode-alist)) (setq auto-mode-alist (cons '("\\.mdt$" . gfm-mode) auto-mode-alist)) (setq auto-mode-alist (cons '("\\.markdown$" . gfm-mode) auto-mode-alist))
The important thing is to add 'gfm-mode
before "markdown-mode.el"
in the autoload
command.