Update LICENSE to mention "or later"

fixes #29

LICENSE

@@ -1 +1,13 @@
-See COPYING.LESSER and COPYING.
+This program is free software: you can redistribute it and/or modify
+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 Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with this program, see COPYING.LESSER and COPYING. 
+If not, see <http://www.gnu.org/licenses/>.