Feature request: optional welcome message in contract

[bligny]

See post on forum: https://groups.google.com/forum/#!topic/mountebank-discuss/0FrlvPErRR0

The idea is to augment (at least for "tcp" protocol) the current contract with an optional welcome message that will be sent spontaneously by mountebank as soon as the connection is established.

IMHO, this would open mountebank to more protocols such as NATS (https://nats.io/documentation/internals/nats-protocol/) which requires a preliminary message (see "INFO" message) before beginning request-reply exchanges.