License - update dates and rtf version (used in msi)

Author: samaaron

LICENSE.md

@@ -5,7 +5,7 @@
 
 The MIT License (MIT)
 
-Copyright (c) 2013, 2014, 2015, 2016 Samuel Aaron ([http://sam.aaron.name](http://sam.aaron.name))
+Copyright (c) 2012 - 2020 Samuel Aaron and contributors (sam@sonic-pi.net)
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal