Update license copyright date to 2018

pdaalder · web-flow · commit ad1e8a84f355 · 2018-02-20T15:37:27.000+01:00
diff --git a/LICENSE b/LICENSE
@@ -1,6 +1,6 @@
 The MIT License (MIT)
 
-Copyright (C) 2011-2017 WP-CLI Development Group (https://github.com/wp-cli/language-command/contributors)
+Copyright (C) 2011-2018 WP-CLI Development Group (https://github.com/wp-cli/language-command/contributors)
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
