nats: use buffered channels to improve performance

[HeavyHorst]

The nats performance improve a lot with this little change:

I changed the sendloop in test.go to this

    for i := 0; i < 10000; i++ {
        msg := []byte(fmt.Sprintf("message %d", i+1))
        wg.Add(3)
        transport.Send("vicechannel1") <- msg
        transport.Send("vicechannel2") <- msg
        transport.Send("vicechannel3") <- msg
    }

to send 10000 messages instead of 100 down each channel

Before:

=== RUN   TestTransport
=== RUN   TestTransport/testStandardTransportBehaviour
=== RUN   TestTransport/testSendChannelsDontBlock
--- PASS: TestTransport (2.34s)
    --- PASS: TestTransport/testStandardTransportBehaviour (2.34s)
    --- PASS: TestTransport/testSendChannelsDontBlock (0.00s)
=== RUN   TestReceive
--- PASS: TestReceive (0.01s)
=== RUN   TestSend
--- PASS: TestSend (0.01s)
PASS

After:

=== RUN   TestTransport
=== RUN   TestTransport/testStandardTransportBehaviour
=== RUN   TestTransport/testSendChannelsDontBlock
--- PASS: TestTransport (0.09s)
    --- PASS: TestTransport/testStandardTransportBehaviour (0.09s)
    --- PASS: TestTransport/testSendChannelsDontBlock (0.00s)
=== RUN   TestReceive
--- PASS: TestReceive (0.01s)
=== RUN   TestSend
--- PASS: TestSend (0.01s)
PASS

[matryer]

Amazing.