Add licence info (GPL)

Fixes #11

flymake-coffee.el

@@ -1,12 +1,27 @@
 ;;; flymake-coffee.el --- A flymake handler for coffee script
-;;
-;;; Author: Steve Purcell <steve@sanityinc.com>
-;;; Homepage: https://github.com/purcell/flymake-coffee
-;;; Version: DEV
-;;; Package-Requires: ((flymake-easy "0.1"))
-;;
+
+;; Copyright (c) 2011-2017 Steve Purcell
+
+;; Author: Steve Purcell <steve@sanityinc.com>
+;; Homepage: https://github.com/purcell/flymake-coffee
+;; Package-Version: 0
+;; Package-Requires: ((flymake-easy "0.1"))
+
+;; 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.
+
+;; 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 this program.  If not, see <http://www.gnu.org/licenses/>.
+
 ;;; Commentary:
-;;
+
 ;; Based in part on http://d.hatena.ne.jp/antipop/20110508/1304838383
 ;;
 ;; Usage: