add server/client to namespace commons

include/client.hpp

@@ -8,6 +8,8 @@
 
 #include "boost/bind.hpp"
 
+namespace commons {
+
 class client {
  public:
   client(boost::asio::io_service& io_service,
@@ -26,3 +28,5 @@ class client {
   std::string message_;
   unsigned short port_;
 };
+
+}  // namespace commons