add Elixir source for tutorial 3

elixir/emit_log.exs

@@ -0,0 +1,14 @@
+{:ok, connection} = AMQP.Connection.open
+{:ok, channel} = AMQP.Channel.open(connection)
+
+message = 
+  case System.argv do
+    []    -> "Hello World!"
+    words -> Enum.join(words, " ")
+  end
+
+AMQP.Exchange.declare(channel, "logs", :fanout)
+AMQP.Basic.publish(channel, "logs", "", message)
+IO.puts " [x] Sent '#{message}'"
+
+AMQP.Connection.close(connection)

elixir/receive_logs.exs

@@ -0,0 +1,21 @@
+defmodule ReceiveLogs do
+  def wait_for_messages(channel) do
+    receive do
+      {:basic_deliver, payload, _meta} ->
+        IO.puts " [x] Received #{payload}"
+
+        wait_for_messages(channel)
+    end
+  end
+end
+
+{:ok, connection} = AMQP.Connection.open
+{:ok, channel} = AMQP.Channel.open(connection)
+
+AMQP.Exchange.declare(channel, "logs", :fanout)
+{:ok, %{queue: queue_name}} = AMQP.Queue.declare(channel, "", exclusive: true)
+AMQP.Queue.bind(channel, queue_name, "logs")
+AMQP.Basic.consume(channel, queue_name, nil, no_ack: true)
+IO.puts " [*] Waiting for messages. To exit press CTRL+C, CTRL+C"
+
+ReceiveLogs.wait_for_messages(channel)