Introduce global state for options so we don't have to pass it around

test/options_test.exs

@@ -2,17 +2,17 @@ defmodule OptionTest do
   use ExUnit.Case, async: true
 
   test "has default options" do
-    options = Options.parse([])
-    refute Map.fetch!(options, :clear_screen)
+    Options.parse([])
+    refute Options.clear_screen?
   end
 
   test "override clearing of screen" do
-    options = Options.parse(["--clear-screen"])
-    assert Map.fetch!(options, :clear_screen)
+    Options.parse(["--clear-screen"])
+    assert Options.clear_screen?
   end
 
   test "ignores unknown options" do
     options = Options.parse(["--foo"])
-    refute Map.fetch!(options, :clear_screen)
+    refute Options.clear_screen?
   end
 end