update hex_core dependency from branch

mix.lock

@@ -9,7 +9,7 @@
   "git_diff": {:git, "https://github.com/hexpm/git_diff.git", "453ed1933e87e47c2debef1b5b77a0dc4a1c3fb7", [branch: "emj/stream"]},
   "goth": {:hex, :goth, "1.2.0", "92d6d926065a72a7e0da8818cc3a133229b56edf378022c00d9886c4125ce769", [:mix], [{:httpoison, "~> 0.11 or ~> 1.0", [hex: :httpoison, repo: "hexpm", optional: false]}, {:jason, "~> 1.1", [hex: :jason, repo: "hexpm", optional: false]}, {:joken, "~> 2.0", [hex: :joken, repo: "hexpm", optional: false]}], "hexpm", "4974932ab3b782c99a6fdeb0b968ddd61436ef14de5862bd6bb0227386c63b26"},
   "hackney": {:hex, :hackney, "1.15.2", "07e33c794f8f8964ee86cebec1a8ed88db5070e52e904b8f12209773c1036085", [:rebar3], [{:certifi, "2.5.1", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "6.0.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "1.0.1", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~>1.1", [hex: :mimerl, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "1.1.5", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}], "hexpm", "e0100f8ef7d1124222c11ad362c857d3df7cb5f4204054f9f0f4a728666591fc"},
-  "hex_core": {:git, "https://github.com/RudolfMan/hex_core.git", "8295d4b67f7d461a991fa34507b0e2c74a3201ea", [branch: "unpack-list-of-files"]},
+  "hex_core": {:git, "https://github.com/RudolfMan/hex_core.git", "7886b9c8a0da00c5d021c739a36f80665716ceac", [branch: "unpack-list-of-files"]},
   "html_entities": {:hex, :html_entities, "0.5.0", "40f5c5b9cbe23073b48a4e69c67b6c11974f623a76165e2b92d098c0e88ccb1d", [:mix], [], "hexpm", "8e9186e1873bea1067895f6a542b59df6c9fcf3b516ba272eeff3ea0c7b755cd"},
   "httpoison": {:hex, :httpoison, "1.6.2", "ace7c8d3a361cebccbed19c283c349b3d26991eff73a1eaaa8abae2e3c8089b6", [:mix], [{:hackney, "~> 1.15 and >= 1.15.2", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm", "aa2c74bd271af34239a3948779612f87df2422c2fdcfdbcec28d9c105f0773fe"},
   "idna": {:hex, :idna, "6.0.0", "689c46cbcdf3524c44d5f3dde8001f364cd7608a99556d8fbd8239a5798d4c10", [:rebar3], [{:unicode_util_compat, "0.4.1", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "4bdd305eb64e18b0273864920695cb18d7a2021f31a11b9c5fbcd9a253f936e2"},