Merge branch 'license' of diffpy-release

* Update license year to 2019

Author: pavoljuhas

LICENSE.txt

@@ -10,7 +10,7 @@ Copyright (c) 2006-2007, Board of Trustees of Michigan State University
 Copyright (c) 2008-2012, The Trustees of Columbia University in the City
     of New York
 
-Copyright (c) 2014-2017, Brookhaven Science Associates, Brookhaven National
+Copyright (c) 2014-2019, Brookhaven Science Associates, Brookhaven National
     Laboratory