feat(client): allow support of blocking notification

[sebastienfr]

Closes #8 support of blocking notification in amqp. Missing some tests. I was not able to block rabbit server by limiting resources to do the testing.

[kron4eg]

Hello @sebastienfr, thanks for contribution!

I have few comments on this:

• please remove .editorconfig file, it doesn't really belong to this feature.
• chan *amqp.Blocking — no need for pointer here, original amqp lib exposed amqp.Blocking, not pointer to it.
• You've forgot to initialize (*Client).blocking channel. Some buffering will be nice to have.
• method (*Client).reportBlocking used only once and without checking return, it will be better to inline its body and remove method.

like this:

case blocking := <-chanBlocking:
    select {
    case c.blocking <- blocking:
    default:
    }
}

[sebastienfr]

Thanks for your careful review. Here are the changes. I was able to test it by running a rabbitmq in a docker container and allocating only 300m of memory to my docker-machine and it works fine. I'll got the blocking true / low memory.

[kron4eg]

@sebastienfr awesome! Looks good.

@pavel-d please merge this.