Missing option for encoding in buffer reads.

[Gulars2000]

Hi i had troubles when doing parralel sessions, afers some troubleshoooring i realised that your buf.toString(), statements didnt incllude encoding.
Since telnet is 7 bit ascii this created a few weird issues.
i added encoding ascii to all 3 empty buf.toString() statements and it seemed to solve the issues.

[mkozjak]

Care to do a PR?

[mkozjak]

This solution should be done in a way to respect telnet negotiations for charset, eg. IAC SB CHARSET ACCEPT "UTF-8" IAC SE.