towards an example client

connects and does nothing, passes supported
negotiation options.

keyboard i/o is not yet handled.
export client.py library exports (TelnetClient)
remove cmd-line use, moved to examples/client.py
pep8
increase sb buffer, align by power of 2
escape_iac -> _escape_iac, unexport
distinguish EOR from CMD_EOR
moar _escape_iac
refactor NEW_ENVIRON support, include client-end
maor EOR / EOR_CMD refactors
more NEW_ENVIRON refactoring, byte option consts
pep8, docfix, format string {} preferred
refactoring of send opts for pending/True/False

more assertions of server/client end
more clear about why send was not send in log
True/False returns more implicit
pep8 and tulip->asyncio, (works again..)
handle eof_received just as server, return False

discovered self.close() only corrus when this method returns False,
perhaps not well documented!
EOR-CMD_EOR fix, return False on eof_received
remove duplicated line
EOR -> CMD_EOR
use name_command in assertion error
pending_option fix for DO + LOGOUT