Added license header

Author: jgbeninger

README.md

@@ -1,3 +1,18 @@
+Copyright (C) 2021 Julian Rossbroich, Daniel Trotter, John Beninger, Richard Naud
+
+    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 <https://www.gnu.org/licenses/>.
+
 # Spike Response Plasticity
 
 Implementation of a linear-nonlinear model of short-term plasticity as described in