Removed duplicate #includes

Summary:
Removed duplicate #includes.

Facebook: The removals were examined by hand: several duplicate includes
were not removed because they were/seemed to
be in different preprocessor branches of the source.

@override-unit-failures

Test Plan: arc unit

Reviewed By: robbert@fb.com

FB internal diff: D1136491

folly/test/ApplyTupleTest.cpp

 /*
- * Copyright 2013 Facebook, Inc.
+ * Copyright 2014 Facebook, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,7 +19,6 @@
 #include "folly/ApplyTuple.h"
 #include <gtest/gtest.h>
 
-#include <iostream>
 #include <memory>
 
 namespace {