Channels will now reset their unconfirmed delivery tag set after

recovery.

GitHub issue: [ruby-amqp#406](ruby-amqp#406)

Contributed by Bill Ruddock.

GitHub issue: [ruby-amqp#383](ruby-amqp#383).

Contributed by Jeremy Heiler.

Since transport is replaced by a recovering connection
anyway, and this produces confusing errors up the stack.

GitHub issue: [ruby-amqp#359](ruby-amqp#359)

Contributed by Donal McBreen.

Client-Provided Session `:properties` will now be merged with defaults
instead of replacing them. This makes it much more convenient to
override a single key.

`RABBITMQ_URL` no longer will be used if any other
connection options are provided. This makes it possible
to use `RABBITMQ_URL` for some connections and options
for others in a single OS process.

GitHub issue: [ruby-amqp#403](ruby-amqp#403)

Contributed by Jimmy Petersen.