Add RabbitMQ support

[Jisu-Woniu]

As is suggested by SASTOJ developers, a RabbitMQ plugin will fit better in the current SASTOJ architecture.

The plugin should support:

• Fetching test cases from an MQ that is amqp 0-9-1 compatible, like RabbitMQ
• Run the test cases through the given Judger instance
• Send the judge result back in a streaming manner

The demos in other languages can be found in RabbitMQ Docs.