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

example/value.cpp

@@ -5,7 +5,7 @@
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 //
 
-#include "boost/mysql/value.hpp"
+#include <boost/mysql/value.hpp>
 #include <iostream>
 
 #define ASSERT(expr) \