Roll copyright dates.

Author: gregturn

LICENSE.txt

@@ -190,7 +190,7 @@ APPENDIX: How to apply the Apache License to your work.
    same "printed page" as the copyright notice for easier
    identification within third-party archives.
 
-Copyright 2019 Greg L. Turnquist
+Copyright 2019-2020 Greg L. Turnquist
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.