AU: Class to perform delta updates.

A class to perform delta updates and the associated unittests. Also,
change the delta diff generator executable to be able to apply a
delta, which is handy for debugging.

TEST=Attached unit test, hand-tested on real build images
BUG=552

Review URL: http://codereview.chromium.org/1718001
diff --git a/filesystem_iterator_unittest.cc b/filesystem_iterator_unittest.cc
index da14b87..676d91f 100644
--- a/filesystem_iterator_unittest.cc
+++ b/filesystem_iterator_unittest.cc
@@ -8,8 +8,8 @@
 #include <set>
 #include <string>
 #include <vector>
-#include "base/string_util.h"
 #include <gtest/gtest.h>
+#include "base/string_util.h"
 #include "update_engine/filesystem_iterator.h"
 #include "update_engine/test_utils.h"
 #include "update_engine/utils.h"