After a read completes it's possible more data is pending so issue an
immediate read again to pick this up quickly.

- enable sending and receiving of raw array buffers in addition to
  strings.

- add a read poll interval and set it to 15ms by default to detect
  and handle quickly when a message is pending.

- also, detect a disconnected state and add call registration for
  disconnect events.

Import upstream code from Chrome extension telnet demo:
https://raw.github.com/GoogleChrome/chrome-app-samples/0ce28768087863c08aa04a2b9b27bd50796a77ec/telnet/tcp-client.js