header: change date to 2016

Update LICENCE header year to 2016.

.header

@@ -1,4 +1,4 @@
-// Copyright 2014 CoreOS, Inc.
+// Copyright 2016 CoreOS, Inc.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.