use present for copyright range

LICENSE

@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (c) 2013-2017 Yuxi Evan You
+Copyright (c) 2013-present, Yuxi (Evan) You
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -98,4 +98,4 @@ Details changes for each release are documented in the [release notes](https://g
 
 [MIT](http://opensource.org/licenses/MIT)
 
-Copyright (c) 2013-2016 Evan You
+Copyright (c) 2013-present, Yuxi (Evan) You