Separate connection process into its own method

This allows us to easily call the connect method to reconnect with the same
parameters used to initialize the Connection instance. This can later be used to
automatically reconnect if the connection gets closed for some reason.
Reorganize instance variables

No functional changes
Keep track of time last heartbeat was sent/received
Bump version
Bump version

Bumped to 0.9.2 to avoid confusion with the AMQP protocol version that this
library supports.