Take connection_name from options parameter and make it a new standard

[ono]

Additional work for #165. Taking connection_name from options is more intuitive and concise for Connection.open. Therefore this PR makes it as a new standard while supporting a backward compatibility.

1. Support connection_name option in Connection.open/1 and Connection.open/2
2. Deprecated connection_name parameter on Connection.open/* and recommend to use options
3. Still support connection_name parameter to support backward compatibility

[ono]

I have been thinking about connection_name v.s. name as an option key for this. I personally prefer name as it's obvious enough what it is for and connection_ prefix seems to be unnecessary.

However I keep it calling connection_name because:

• the parameter is referred as ConnectionName or ConnName by amqp_client [*1]
• we might want to avoid a chance mixing up with username or hostname

[*1]
https://github.com/rabbitmq/rabbitmq-erlang-client/blob/master/src/amqp_connection.erl#L149

I'm planning to merge and release a new version in this week.

[ono]

Sorry for the delay - I couldn't have spent time on the project.

I also argued again by myself and decided to go for name for the option key instead of connection_name. It looks concise and better and is obvious enough it's a name of the connection you are opening.

AMQP.Connection.open("amqp://guest:guest@localhost", connection_name: "my-connection")
AMQP.Connection.open("amqp://guest:guest@localhost", name: "my-connection")