Updated license

Noticed that the license was wrong after receiving #22.

ox-gfm.el

@@ -1,24 +1,24 @@
 ;;; ox-gfm.el --- Github Flavored Markdown Back-End for Org Export Engine
 
-;; Copyright (C) 2014 Lars Tveito
+;; Copyright (C) 2014-2017 Lars Tveito
 
 ;; Author: Lars Tveito
 ;; Keywords: org, wp, markdown, github
 
 ;; This file is not part of GNU Emacs.
 
-;; GNU Emacs is free software: you can redistribute it and/or modify
+;; This program is free software; you can redistribute it and/or modify
 ;; it under the terms of the GNU General Public License as published by
 ;; the Free Software Foundation, either version 3 of the License, or
 ;; (at your option) any later version.
 
-;; GNU Emacs is distributed in the hope that it will be useful,
+;; This program is distributed in the hope that it will be useful,
 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 ;; GNU General Public License for more details.
 
 ;; You should have received a copy of the GNU General Public License
-;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 ;;; Commentary: