feat(license): Relicense under GPLv3

All further kontemplate source code changes and releases will happen under the GPLv3.

Previous releases are still available under the MIT license.

main.go

@@ -1,3 +1,18 @@
+// Copyright (C) 2016-2017  Vincent Ambo <mail@tazj.in>
+//
+// Kontemplate 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/>.
+
 package main
 
 import (