Removes trailing slash on default url, which does not work with default rabbit setup

The default url is in place to work with the default RabbitMQ setup, but the trailing slash is incompatible.

Error message is as follows:
```
amqp-1.1.7/lib/amqp/session.rb:199:in `initialize': AMQP broker closed TCP 
connection before authentication succeeded: this usually means authentication 
failure due to misconfiguration.
```