Switch to LGPL (from GPL) - closes #3

LICENCE

@@ -1,15 +1,14 @@
 Copyright (C) 2010-2012 Tim Cuthbertson
 
 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.
+it under the terms of the GNU Lesser 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.
+GNU Lesser General Public License for more details.
 
-You should have received a copy of the GNU General Public License
+You should have received a copy of the GNU Lesser General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
-