add approved license in the COPYING file

COPYING

+                   Copyright (C) 2015, UChicago Argonne, LLC
+                              All Rights Reserved
+
+                              Generic IO (ANL-15-066)
+                    Hal Finkel, Argonne National Laboratory
+
+                             OPEN SOURCE LICENSE
+
+Under the terms of Contract No. DE-AC02-06CH11357 with UChicago Argonne, LLC,
+the U.S. Government retains certain rights in this software.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+  1. Redistributions of source code must retain the above copyright notice,
+     this list of conditions and the following disclaimer.
+
+  2. Redistributions in binary form must reproduce the above copyright notice,
+     this list of conditions and the following disclaimer in the documentation
+     and/or other materials provided with the distribution.
+
+  3. Neither the names of UChicago Argonne, LLC or the Department of Energy nor
+     the names of its contributors may be used to endorse or promote products
+     derived from this software without specific prior written permission.
+
+********************************************************************************
+
+                                 DISCLAIMER
+THE SOFTWARE IS SUPPLIED “AS IS” WITHOUT WARRANTY OF ANY KIND.  NEITHER THE
+UNTED STATES GOVERNMENT, NOR THE UNITED STATES DEPARTMENT OF ENERGY, NOR
+UCHICAGO ARGONNE, LLC, NOR ANY OF THEIR EMPLOYEES, MAKES ANY WARRANTY, EXPRESS
+OR IMPLIED, OR ASSUMES ANY LEGAL LIABILITY OR RESPONSIBILITY FOR THE ACCURACY,
+COMPLETENESS, OR USEFULNESS OF ANY INFORMATION, DATA, APPARATUS, PRODUCT, OR
+PROCESS DISCLOSED, OR REPRESENTS THAT ITS USE WOULD NOT INFRINGE PRIVATELY
+OWNED RIGHTS.
+
+********************************************************************************
+