Remove copyright years

Author: anishathalye

README.md

@@ -89,7 +89,7 @@ requests are much appreciated!
 
 ## License
 
-Copyright (c) 2016-2018 by the authors (see [AUTHORS.txt][authors]). Released
+Copyright (c) by the authors (see [AUTHORS.txt][authors]). Released
 under GPLv3. See [LICENSE.txt][license] for details.
 
 [issue]: https://github.com/anishathalye/offix/issues/new