Use separate connections for producers, consumers, etc.

[rnowling-memphis]

Currently, producers and consumers all share a single connection to the Memphis broker. The user creates a Memphis object and calls connect() to establish a connection. When producers and consumers are created with Memphis.producer() and Memphis.consumer(), the connection object is passed to the constructors of the Producer and Consumer classes.

Should we be doing this? Or should each new producer or consumer get its own connection?