Update copyright date range

ctrueden · ctrueden · commit e4ebaf2b74d3 · 2020-11-30T14:25:10.000-06:00
diff --git a/LICENSE.txt b/LICENSE.txt
@@ -1,4 +1,4 @@
-Copyright (C) 2013 - 2018 Board of Regents of the University of
+Copyright (C) 2013 - 2020 Board of Regents of the University of
 Wisconsin-Madison.
 
 Licensed under the Apache License, Version 2.0 (the "License");

Original file line number	Diff line number	Diff line change
`@@ -1,4 +1,4 @@`
`1`		`-Copyright (C) 2013 - 2018 Board of Regents of the University of`
	`1`	`+Copyright (C) 2013 - 2020 Board of Regents of the University of`
`2`	`2`	`Wisconsin-Madison.`
`3`	`3`
`4`	`4`	`Licensed under the Apache License, Version 2.0 (the "License");`