Fix copyright headers in source files

Still need to add some missing headers and an AUTHORS file.

See #1646

parser/frontmatter.go

@@ -1,4 +1,4 @@
-// Copyright © 2013 Steve Francia <spf@spf13.com>.
+// Copyright 2015 The Hugo Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.