TCP Connection API

[NiteshKant]

This issue is for discussing the API of a TCP connection required by both client(#2) and server(#3)

Intention

To define how a TCP connection must be modeled using reactive-streams-jvm SPI.

Discussion points

• How does one read from a connection?
• How does one write to a connection?
• When does a connection get closed?
• Should we model a flush() operation to batch multiple writes?