Update LICENSE.txt (#139)

I think this reflects better the current state of affairs, and is in line with what other projects do.

Author: andreasbovens

LICENSE.txt

@@ -186,7 +186,8 @@
       same "printed page" as the copyright notice for easier
       identification within third-party archives.
 
-   Copyright 2016 Andreas Bovens
+   Copyright 2016 Opera Software AS
+   Copyright 2016 The pwa.rocks Authors
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.