Feature: wait for TCP services

[langston-barrett]

Reads and matches from the connection concurrently.
Reads and writes are restricted by timeouts.

Fixes #2, #3

tested manually with these pairs of commands:

term1 $ nc -l -p 1234
term2 $ ./smlr-bin tcp localhost:1234
# succeeds

term1 $ nc -l -p 1234
term2 $ ./smlr-bin tcp --iotimeout 0s --content "pong" localhost:1234
# fails with timeout

term1 $ echo "pong" | nc -l -p 1234
term2 $ ./smlr-bin tcp --content "pong" localhost:1234
# succeeds

term1 $ echo "pong etc" | nc -l -p 1234
term2 $ ./smlr-bin tcp --content "pong" localhost:1234
# succeeds

term1 $ echo "pong etc" | nc -l -p 1234
term2 $ ./smlr-bin tcp --content "pong" --complete localhost:1234
# fails on timeout --- no EOF recieved

term1 $ echo "pong" | nc -l -p 1234
term2 $ ./smlr-bin tcp --content "pong" --complete localhost:1234
# fails on timeout --- no EOF recieved