add namespace for requester

Change-Id: I3de037dffd702edff9f87a87e8e684161db3d329
diff --git a/src/configuration.hpp b/src/configuration.hpp
index d13397c..3671e20 100644
--- a/src/configuration.hpp
+++ b/src/configuration.hpp
@@ -142,6 +142,8 @@
 
 } // namespace ca
 
+namespace requester {
+
 /**
  * @brief Represents Client configuration
  *
@@ -178,6 +180,7 @@
   std::list<CaProfile> m_caItems;
 };
 
+} // namespace requester
 } // namespace ndncert
 } // namespace ndn