Bump cowboy and cowlib (#99)

See https://ninenines.eu/articles/cowboy-2.12.0/

Projects depending on cowboy_plug get to those versions of the
transitive dependencies anyway when upgrading.

mix.lock

@@ -1,8 +1,8 @@
 %{
   "certifi": {:hex, :certifi, "2.9.0", "6f2a475689dd47f19fb74334859d460a2dc4e3252a3324bd2111b8f0429e7e21", [:rebar3], [], "hexpm", "266da46bdb06d6c6d35fde799bcb28d36d985d424ad7c08b5bb48f5b5cdd4641"},
-  "cowboy": {:hex, :cowboy, "2.11.0", "356bf784599cf6f2cdc6ad12fdcfb8413c2d35dab58404cf000e1feaed3f5645", [:make, :rebar3], [{:cowlib, "2.12.1", [hex: :cowlib, repo: "hexpm", optional: false]}, {:ranch, "1.8.0", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm", "0fa395437f1b0e104e0e00999f39d2ac5f4082ac5049b67a5b6d56ecc31b1403"},
+  "cowboy": {:hex, :cowboy, "2.12.0", "f276d521a1ff88b2b9b4c54d0e753da6c66dd7be6c9fca3d9418b561828a3731", [:make, :rebar3], [{:cowlib, "2.13.0", [hex: :cowlib, repo: "hexpm", optional: false]}, {:ranch, "1.8.0", [hex: :ranch, repo: "hexpm", optional: false]}], "hexpm", "8a7abe6d183372ceb21caa2709bec928ab2b72e18a3911aa1771639bef82651e"},
   "cowboy_telemetry": {:hex, :cowboy_telemetry, "0.4.0", "f239f68b588efa7707abce16a84d0d2acf3a0f50571f8bb7f56a15865aae820c", [:rebar3], [{:cowboy, "~> 2.7", [hex: :cowboy, repo: "hexpm", optional: false]}, {:telemetry, "~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "7d98bac1ee4565d31b62d59f8823dfd8356a169e7fcbb83831b8a5397404c9de"},
-  "cowlib": {:hex, :cowlib, "2.12.1", "a9fa9a625f1d2025fe6b462cb865881329b5caff8f1854d1cbc9f9533f00e1e1", [:make, :rebar3], [], "hexpm", "163b73f6367a7341b33c794c4e88e7dbfe6498ac42dcd69ef44c5bc5507c8db0"},
+  "cowlib": {:hex, :cowlib, "2.13.0", "db8f7505d8332d98ef50a3ef34b34c1afddec7506e4ee4dd4a3a266285d282ca", [:make, :rebar3], [], "hexpm", "e1e1284dc3fc030a64b1ad0d8382ae7e99da46c3246b815318a4b848873800a4"},
   "earmark_parser": {:hex, :earmark_parser, "1.4.39", "424642f8335b05bb9eb611aa1564c148a8ee35c9c8a8bba6e129d51a3e3c6769", [:mix], [], "hexpm", "06553a88d1f1846da9ef066b87b57c6f605552cfbe40d20bd8d59cc6bde41944"},
   "ex_doc": {:hex, :ex_doc, "0.31.2", "8b06d0a5ac69e1a54df35519c951f1f44a7b7ca9a5bb7a260cd8a174d6322ece", [:mix], [{:earmark_parser, "~> 1.4.39", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_c, ">= 0.1.1", [hex: :makeup_c, repo: "hexpm", optional: true]}, {:makeup_elixir, "~> 0.14", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1", [hex: :makeup_erlang, repo: "hexpm", optional: false]}], "hexpm", "317346c14febaba9ca40fd97b5b5919f7751fb85d399cc8e7e8872049f37e0af"},
   "hackney": {:hex, :hackney, "1.18.1", "f48bf88f521f2a229fc7bae88cf4f85adc9cd9bcf23b5dc8eb6a1788c662c4f6", [:rebar3], [{:certifi, "~>2.9.0", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "~>6.1.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "~>1.0.0", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "~>1.1", [hex: :mimerl, repo: "hexpm", optional: false]}, {:parse_trans, "3.3.1", [hex: :parse_trans, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "~>1.1.0", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}, {:unicode_util_compat, "~>0.7.0", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm", "a4ecdaff44297e9b5894ae499e9a070ea1888c84afdd1fd9b7b2bc384950128e"},