Fix autoload.php generator

src/Composer/Autoload/AutoloadGenerator.php

@@ -39,11 +39,11 @@ class AutoloadGenerator
     {
         $autoloads = $this->parseAutoloads();
 
-        $file = <<<'EOF'
-<?php
-// autoload.php generated by composer
+        $file = file_get_contents(__DIR__.'/ClassLoader.php');
 
-namespace Composer\Autoload;
+        $file .= <<<'EOF'
+
+// autoload.php generated by composer
 
 $loader = new ClassLoader();
 
@@ -67,8 +67,6 @@ $loader->register();
 
 EOF;
 
-        $file .= file_get_contents(__DIR__.'/ClassLoader.php');
-
         file_put_contents($targetFilename, $file);
     }