Cleanup iostream includes

Change-Id: I16dd945998463975b140c7a010d64a112f95d8ba
diff --git a/src/name-component.cpp b/src/name-component.cpp
index 045d5f2..6bccced 100644
--- a/src/name-component.cpp
+++ b/src/name-component.cpp
@@ -31,6 +31,7 @@
 #include "util/string-helper.hpp"
 
 #include <boost/algorithm/string/trim.hpp>
+#include <sstream>
 
 namespace ndn {
 namespace name {