use poper emacs namespace, move keys to dedicated minor mode

lang/markdown.el

@@ -0,0 +1,27 @@
+;;; markdown -- summary
+;;; Commentary:
+;;; Code:
+
+(require 'icejam-pkg-prog-mode "$HOME/.emacs.d/pkg/prog-mode.el")
+
+(use-package markdown-mode
+  :ensure t
+  :defer t
+  :init (setq-default markdown-command "pandoc"))
+
+(defun activate-markdown-mode ()
+  "Reconfigure markdown mode for your own purposes."
+  (set-indent 2)
+  (column-enforce-n 80)
+
+  ;; Markdown mode reuses my bindings, remove them.
+  (define-key markdown-mode-map (kbd "C-c <left>") nil)
+  (define-key markdown-mode-map (kbd "C-c <right>") nil)
+  (define-key markdown-mode-map (kbd "C-c <up>") nil)
+  (define-key markdown-mode-map (kbd "C-c <down>") nil)
+  (define-key markdown-mode-map (kbd "C-c C-v") 'markdown-preview))
+
+(add-hook 'markdown-mode-hook 'activate-markdown-mode)
+
+(provide 'icejam-lang-markdown)
+;;; markdown.el ends here