Fixes #2441: Remove (deprecated) registerExtension support.

src/coffee-script.coffee

@@ -15,13 +15,10 @@ vm               = require 'vm'
 stripBOM = (content) ->
   if content.charCodeAt(0) is 0xFEFF then content.substring 1 else content
 
-# TODO: Remove registerExtension when fully deprecated.
 if require.extensions
   require.extensions['.coffee'] = (module, filename) ->
     content = compile stripBOM(fs.readFileSync filename, 'utf8'), {filename}
     module._compile content, filename
-else if require.registerExtension
-  require.registerExtension '.coffee', (content) -> compile content
 
 # The current CoffeeScript version number.
 exports.VERSION = '1.3.3'