Ability to replay lines from STDIN

[berkes]

webmocket < ./file_with_ws_message_per_line

Difficulty is that we should start outputting to the Websocket only after a client connects, or else that client will miss lines until it is successfully connected.

Acceptance criteria:

Given a file with two lines:
hello from server line 1
hello from server line 2
When I run websocket and pipe that file into STDIN
And when I then connect a client to the WS port
Then I expect to receive the piped in messages after a small (<1s) delay.