Bump version to 2.0.0
Bump version to 2.0.0

Breaking changes:
* Ruby 2.5 and 2.6 are no longer supported.
* OpenTracing has been replaced with OpenTelemetry.
* `Freddy#deliver_with_response` no longer publishes to topic queue
  (this means that these messages cannot be listened to with
  `Freddy#tap_into`).

salemove/freddy