add Elixir tutorial 1

Prior to this commit, the RabbitMQ tutorials contained no Elixir
examples. One _could_ look at the Erlang examples and adapt them, but
that certainly does not result in idiomatic Elixir. This commit adds the
first tutorial and an Elixir project file specifying the `amqp` library
as the dependency for communicating with RabbitMQ via idiomatic Elixir.

elixir/.gitignore

@@ -0,0 +1,4 @@
+.mix_tasks
+mix.lock
+/_build
+/deps

elixir/mix.exs

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+defmodule RabbitmqTutorials.Mixfile do
+  use Mix.Project
+
+  def project do
+    [app: :rabbitmq_tutorials,
+     version: "0.0.1",
+     elixir: "~> 1.1",
+     build_embedded: Mix.env == :prod,
+     start_permanent: Mix.env == :prod,
+     deps: deps]
+  end
+
+  # Configuration for the OTP application
+  #
+  # Type "mix help compile.app" for more information
+  def application do
+    [applications: [:logger, :amqp]]
+  end
+
+  # Dependencies can be Hex packages:
+  #
+  #   {:mydep, "~> 0.3.0"}
+  #
+  # Or git/path repositories:
+  #
+  #   {:mydep, git: "https://github.com/elixir-lang/mydep.git", tag: "0.1.0"}
+  #
+  # Type "mix help deps" for more examples and options
+  defp deps do
+    [
+      {:amqp, "~> 0.1.4"},
+    ]
+  end
+end

elixir/receive.exs

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+defmodule Receive do
+  def wait_for_messages do
+    receive do
+      {:basic_deliver, payload, _meta} ->
+        IO.puts " [x] Received #{payload}"
+        wait_for_messages
+    end
+  end
+end
+
+{:ok, connection} = AMQP.Connection.open
+{:ok, channel} = AMQP.Channel.open(connection)
+AMQP.Queue.declare(channel, "hello")
+AMQP.Basic.consume(channel, "hello", nil, no_ack: true)
+IO.puts " [*] Waiting for messages. To exit press CTRL+C, CTRL+C"
+
+Receive.wait_for_messages

elixir/send.exs

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+{:ok, connection} = AMQP.Connection.open
+{:ok, channel} = AMQP.Channel.open(connection)
+AMQP.Queue.declare(channel, "hello")
+AMQP.Basic.publish(channel, "", "hello", "Hello World!")
+IO.puts " [x] Sent 'Hello World!'"
+AMQP.Connection.close(connection)