Update NOTICE.txt

NOTICE.txt

@@ -1,5 +1,5 @@
 Mattermost Platform Preview 
-Copyright 2015 SpinPunch, Inc. 
+© 2015 Spinpunch, Inc.  All Rights Reserved.  See LICENSE.txt for license information.
 
 This product contains a modified portion of 'draw2d', a Go library to draw 2d geometrical forms on images by Laurent Le Goff