update license

hdf5plugin_sz/LICENSE

@@ -38,9 +38,10 @@ ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 ===================================================================================
-HDF5 compression filter plugin
-Copyright 2013-2015 by The HDF Group.
+This software is based on the source of HDF5 compression filter plugin
+https://github.com/nexusformat/HDF5-External-Filter-Plugins
 
+Copyright 2013-2015 by The HDF Group.
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without