Update contributing guide, bump year

Author: sagikazarmark

CONDUCT.md

@@ -0,0 +1 @@
+Please see http://docs.php-http.org/en/latest/development/contributing.html

CONTRIBUTING

@@ -1,4 +1,4 @@
-Copyright (c) 2015 PHP HTTP Team <team@php-http.org>
+Copyright (c) 2015-2016 PHP HTTP Team <team@php-http.org>
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

CONTRIBUTING.md

@@ -44,7 +44,7 @@ $ composer test
 
 ## Contributing
 
-Please see [CONTRIBUTING](CONTRIBUTING.md) and [CONDUCT](CONDUCT.md) for details.
+Please see our [contributing guide](http://docs.php-http.org/en/latest/development/contributing.html).
 
 
 ## Security