Tweak copyright years for less maintenance

Author: Lars-Magnus Skog

README.md

@@ -299,7 +299,7 @@ A large portion of the Windows support comes from code by [Krzysztof Kowalczyk](
 
 ## License
 
-Copyright © 2012-2018 `leveldown` [contributors](https://github.com/level/community#contributors).
+Copyright © 2012-present `leveldown` [contributors](https://github.com/level/community#contributors).
 
 `leveldown` is licensed under the MIT license. All rights not explicitly granted in the MIT license are reserved. See the included `LICENSE.md` file for more details.