Add a progress bar that also displays the number of koans.

test/display_test.exs

@@ -0,0 +1,18 @@
+defmodule DisplayTest do
+  use ExUnit.Case
+
+  test "puts counter on the right until half the koans are complete" do
+    bar = Display.progress_bar(%{total: 12, current: 3})
+    assert bar == "|==========>        (3/12)              |"
+  end
+
+  test "puts the counter on the left after half the koans are complete" do
+    bar = Display.progress_bar(%{total: 12, current: 10})
+    assert bar == "|(10/12)========================>       |"
+  end
+
+  test "full bar" do
+    bar = Display.progress_bar(%{total: 12, current: 12})
+    assert bar == "|(12/12)===============================>|"
+  end
+end