GitHub license update

LICENSE.txt

-Akvo, a surface NMR workbench
-Copyright (C) 2014-2017 Trevor P. Irons  
-Copyright (C) 2017 M. Andrew Kass  
-
 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
 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+Akvo, a surface NMR workbench
+Copyright (C) 2014-2017 Trevor P. Irons  
+Copyright (C) 2017 M. Andrew Kass  
+