Fix header error by using hackney 1.7 (#263)

Closes #259

mix.exs

@@ -58,7 +58,7 @@ defmodule Bamboo.Mixfile do
       {:floki, "~> 0.8", only: :test},
       {:ex_doc, "~> 0.9", only: :dev},
       {:earmark, ">= 0.0.0", only: :dev},
-      {:hackney, "~> 1.6"},
+      {:hackney, "~> 1.7"},
       {:poison, ">= 1.5.0"},
     ]
   end

mix.lock

@@ -1,4 +1,4 @@
-%{"certifi": {:hex, :certifi, "0.4.0", "a7966efb868b179023618d29a407548f70c52466bf1849b9e8ebd0e34b7ea11f", [:rebar3], []},
+%{"certifi": {:hex, :certifi, "1.0.0", "1c787a85b1855ba354f0b8920392c19aa1d06b0ee1362f9141279620a5be2039", [:rebar3], []},
   "cowboy": {:hex, :cowboy, "1.0.4", "a324a8df9f2316c833a470d918aaf73ae894278b8aa6226ce7a9bf699388f878", [:make, :rebar], [{:cowlib, "~> 1.0.0", [hex: :cowlib, optional: false]}, {:ranch, "~> 1.0", [hex: :ranch, optional: false]}]},
   "cowlib": {:hex, :cowlib, "1.0.2", "9d769a1d062c9c3ac753096f868ca121e2730b9a377de23dec0f7e08b1df84ee", [:make], []},
   "earmark": {:hex, :earmark, "1.0.1", "2c2cd903bfdc3de3f189bd9a8d4569a075b88a8981ded9a0d95672f6e2b63141", [:mix], []},
@@ -7,8 +7,8 @@
   "excoveralls": {:hex, :excoveralls, "0.5.6", "35a903f6f78619ee7f951448dddfbef094b3a0d8581657afaf66465bc930468e", [:mix], [{:exjsx, "~> 3.0", [hex: :exjsx, optional: false]}, {:hackney, ">= 0.12.0", [hex: :hackney, optional: false]}]},
   "exjsx": {:hex, :exjsx, "3.2.0", "7136cc739ace295fc74c378f33699e5145bead4fdc1b4799822d0287489136fb", [:mix], [{:jsx, "~> 2.6.2", [hex: :jsx, optional: false]}]},
   "floki": {:hex, :floki, "0.10.1", "1e36c04264396699f02640e4f88ee92c3459a9286795f54c860aec9204bfcbf2", [:mix], [{:mochiweb_html, "~> 2.15", [hex: :mochiweb_html, optional: false]}]},
-  "hackney": {:hex, :hackney, "1.6.1", "ddd22d42db2b50e6a155439c8811b8f6df61a4395de10509714ad2751c6da817", [:rebar3], [{:certifi, "0.4.0", [hex: :certifi, optional: false]}, {:idna, "1.2.0", [hex: :idna, optional: false]}, {:metrics, "1.0.1", [hex: :metrics, optional: false]}, {:mimerl, "1.0.2", [hex: :mimerl, optional: false]}, {:ssl_verify_fun, "1.1.0", [hex: :ssl_verify_fun, optional: false]}]},
-  "idna": {:hex, :idna, "1.2.0", "ac62ee99da068f43c50dc69acf700e03a62a348360126260e87f2b54eced86b2", [:rebar3], []},
+  "hackney": {:hex, :hackney, "1.7.1", "e238c52c5df3c3b16ce613d3a51c7220a784d734879b1e231c9babd433ac1cb4", [:rebar3], [{:certifi, "1.0.0", [hex: :certifi, optional: false]}, {:idna, "4.0.0", [hex: :idna, optional: false]}, {:metrics, "1.0.1", [hex: :metrics, optional: false]}, {:mimerl, "1.0.2", [hex: :mimerl, optional: false]}, {:ssl_verify_fun, "1.1.1", [hex: :ssl_verify_fun, optional: false]}]},
+  "idna": {:hex, :idna, "4.0.0", "10aaa9f79d0b12cf0def53038547855b91144f1bfcc0ec73494f38bb7b9c4961", [:rebar3], []},
   "jsx": {:hex, :jsx, "2.6.2", "213721e058da0587a4bce3cc8a00ff6684ced229c8f9223245c6ff2c88fbaa5a", [:mix, :rebar], []},
   "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [:rebar3], []},
   "mime": {:hex, :mime, "1.0.1", "05c393850524767d13a53627df71beeebb016205eb43bfbd92d14d24ec7a1b51", [:mix], []},
@@ -20,4 +20,4 @@
   "plug": {:hex, :plug, "1.2.0", "496bef96634a49d7803ab2671482f0c5ce9ce0b7b9bc25bc0ae8e09859dd2004", [:mix], [{:cowboy, "~> 1.0", [hex: :cowboy, optional: true]}, {:mime, "~> 1.0", [hex: :mime, optional: false]}]},
   "poison": {:hex, :poison, "2.2.0", "4763b69a8a77bd77d26f477d196428b741261a761257ff1cf92753a0d4d24a63", [:mix], []},
   "ranch": {:hex, :ranch, "1.2.1", "a6fb992c10f2187b46ffd17ce398ddf8a54f691b81768f9ef5f461ea7e28c762", [:make], []},
-  "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.0", "edee20847c42e379bf91261db474ffbe373f8acb56e9079acb6038d4e0bf414f", [:make, :rebar], []}}
+  "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.1", "28a4d65b7f59893bc2c7de786dec1e1555bd742d336043fe644ae956c3497fbe", [:make, :rebar], []}}