updates message buffer's set and append payload methods to allow both std::string and raw array input
Adds raw array send method to connection
fixes typo
Updates constructor field order
moves adaptor functions into endpoint_impl
moves bad_connection error handling into get_con_from_hdl
adds raw array based send adaptors to endpoint
adds documentation and adaptors for connection::close
updates close adaptor to proper connection interface
adds state check to connection::close
simplifies sending close frames
fixes warning
updates write_flag code to be robust and exception/thread safe
cleans up handle_accept error paths