Added support for the BIT type

- Moved socket_connection to a separate include file.
- Clarified Stream requirements.
- Made make_error_code public.
- Updated include styles to match Boost's.
- Moved <boost/myql/mysql.hpp> to <boost/mysql.hpp> to match
conventions.
- Added support for the BIT type.

closes #13
closes #21

test/integration/network_functions/async_callback.cpp

@@ -6,7 +6,7 @@
 //
 
 
-#include "boost/mysql/execute_params.hpp"
+#include <boost/mysql/execute_params.hpp>
 #include "network_functions_impl.hpp"
 #include <boost/asio/use_future.hpp>
 #include <boost/test/unit_test.hpp>