Bump poison from 3.1.0 to 4.0.1

Bumps [poison](https://github.com/devinus/poison) from 3.1.0 to 4.0.1.
- [Release notes](https://github.com/devinus/poison/releases)
- [Commits](devinus/poison@3.1.0...4.0.1)

Signed-off-by: dependabot[bot] <support@dependabot.com>

mix.exs

@@ -40,7 +40,7 @@ defmodule GenRMQ.Mixfile do
       {:amqp, "~> 1.0"},
       {:credo, "~> 0.8", only: :dev},
       {:excoveralls, "~> 0.9.1", only: :test},
-      {:poison, "~> 3.1", only: [:dev, :test]},
+      {:poison, "~> 4.0", only: [:dev, :test]},
       {:earmark, "~> 1.2", only: :dev},
       {:ex_doc, "~> 0.18", only: :dev}
     ]

mix.lock

@@ -16,7 +16,7 @@
   "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [:rebar3], [], "hexpm"},
   "mimerl": {:hex, :mimerl, "1.0.2", "993f9b0e084083405ed8252b99460c4f0563e41729ab42d9074fd5e52439be88", [:rebar3], [], "hexpm"},
   "parse_trans": {:hex, :parse_trans, "3.2.0", "2adfa4daf80c14dc36f522cf190eb5c4ee3e28008fc6394397c16f62a26258c2", [:rebar3], [], "hexpm"},
-  "poison": {:hex, :poison, "3.1.0", "d9eb636610e096f86f25d9a46f35a9facac35609a7591b3be3326e99a0484665", [:mix], [], "hexpm"},
+  "poison": {:hex, :poison, "4.0.1", "bcb755a16fac91cad79bfe9fc3585bb07b9331e50cfe3420a24bcc2d735709ae", [:mix], [], "hexpm"},
   "rabbit_common": {:hex, :rabbit_common, "3.7.7", "c0afdf060c091f43d7d6f58889978a074a7a8e28a5e89b9e40c6a474ba295011", [:make, :rebar3], [{:jsx, "2.8.2", [hex: :jsx, repo: "hexpm", optional: false]}, {:lager, "3.6.3", [hex: :lager, repo: "hexpm", optional: false]}, {:ranch, "1.5.0", [hex: :ranch, repo: "hexpm", optional: false]}, {:ranch_proxy_protocol, "1.5.0", [hex: :ranch_proxy_protocol, repo: "hexpm", optional: false]}, {:recon, "2.3.2", [hex: :recon, repo: "hexpm", optional: false]}], "hexpm"},
   "ranch": {:hex, :ranch, "1.5.0", "f04166f456790fee2ac1aa05a02745cc75783c2bfb26d39faf6aefc9a3d3a58a", [:rebar3], [], "hexpm"},
   "ranch_proxy_protocol": {:hex, :ranch_proxy_protocol, "1.5.0", "e698aaeb590ad504b649dc0d3055abee6caf0b49d3caee1a080ae83b5b499f30", [:rebar3], [{:ranch, "1.5.0", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm"},