Point to CONTRIBUTING.md

Common-Metasploit-Module-Coding-Mistakes.md

@@ -1,3 +1,5 @@
+# Please see [CONTRIBUTING.md](https://github.com/rapid7/metasploit-framework/blob/master/CONTRIBUTING.md) for an authoritative coding guide. This document is out of date and should be consulted ONLY for BAD code examples.
+
 This is a collection of all the bad code we often see in Metasploit modules.  You should avoid them, too.
 
 Note: Some of these examples use puts() for demo purposes, but you should always use print_status / print_error when writing a module.
@@ -195,4 +197,4 @@ Metasploit3.new
 ```ruby
 # https://github.com/rapid7/metasploit-framework/issues/3853
 datastore['BAD'] = 'This is bad.'
-```
+```