Change component name to lowercase

Capitalized component names were only a remnant of camel-cased elixir
modules. Now, with component names being separate, there is no need to
follow this convention. Lower-case arguments are the easiest way to
interact with an application.

lib/cli.ex

@@ -1,6 +1,6 @@
 defmodule Onigumo.CLI do
   @components %{
-    :Downloader => Onigumo.Downloader
+    :downloader => Onigumo.Downloader
   }
 
   def main(argv) do

test/onigumo_cli_test.exs

@@ -9,7 +9,7 @@ defmodule OnigumoCLITest do
 
   describe("Onigumo.CLI.main/1") do
     @tag :tmp_dir
-    test("run CLI with 'Downloader' argument", %{tmp_dir: tmp_dir}) do
+    test("run CLI with 'downloader' argument", %{tmp_dir: tmp_dir}) do
       expect(HTTPoisonMock, :start, fn -> nil end)
       expect(HTTPoisonMock, :get!, length(@urls), &HttpSupport.response/1)
 
@@ -18,7 +18,7 @@ defmodule OnigumoCLITest do
       input_file_content = InputSupport.url_list(@urls)
       File.write!(input_path_tmp, input_file_content)
       File.cd(tmp_dir)
-      Onigumo.CLI.main(["Downloader"])
+      Onigumo.CLI.main(["downloader"])
     end
 
     test("run CLI with invalid argument") do