Move sigils to later in the lessons

While doing this, I also discovered that
there is also a reference to lists in numbers, but
that might a bit easier for someone to grasp, given
the hint that the koan gives, and the output they
see when they run it.

lib/koans/09_map_sets.ex

@@ -0,0 +1,84 @@
+defmodule MapSets do
+  use Koans
+
+  @intro "My name is Set, MapSet."
+
+  @set MapSet.new([1, 2, 3, 4, 5])
+
+  koan "I am very similar to a list" do
+    assert Enum.fetch(@set, 0) == {:ok, ___}
+  end
+
+  koan "However, I do not allow duplication" do
+    new_set = MapSet.new([1, 1, 2, 3, 3, 3])
+
+    assert MapSet.size(new_set) == ___
+  end
+
+  def sorted?(set) do
+    list = MapSet.to_list(set)
+    sorted = Enum.sort(list)
+    list == sorted
+  end
+
+  koan "You cannot depend on my order" do
+    new_set = MapSet.new(1..33)
+    assert sorted?(new_set) == ___
+
+    # Note: The number "33" is actually special here. Erlang uses a different
+    # implementation for maps after 32 elements which does not maintain order.
+    # http://stackoverflow.com/a/40408469
+
+    # What do you think this answer to this assertion is?
+    assert sorted?(@set) == ___
+  end
+
+  koan "Does this value exist in the map set?" do
+    assert MapSet.member?(@set, 3) == ___
+  end
+
+  koan "I am merely another collection but, you can perform some operations on me" do
+    new_set = MapSet.new(@set, fn x -> 3 * x end)
+
+    assert MapSet.member?(new_set, 15) == ___
+    assert MapSet.member?(new_set, 1) == ___
+  end
+
+  koan "Add this value into a map set" do
+    modified_set = MapSet.put(@set, 6)
+
+    assert MapSet.member?(modified_set, 6) == ___
+  end
+
+  koan "Delete this value from the map set" do
+    modified_set = MapSet.delete(@set, 1)
+
+    assert MapSet.member?(modified_set, 1) == ___
+  end
+
+  koan "How large is my map set?" do
+    assert MapSet.size(@set) == ___
+  end
+
+  koan "Are these maps twins?" do
+    new_set = MapSet.new([1, 2, 3])
+
+    assert MapSet.equal?(@set, new_set) == ___
+  end
+
+  koan "I want only the common values in both sets" do
+    intersection_set = MapSet.intersection(@set, MapSet.new([5, 6, 7]))
+
+    assert MapSet.member?(intersection_set, 5) == ___
+  end
+
+  koan "Unify my sets" do
+    new_set = MapSet.union(@set, MapSet.new([1, 5, 6, 7]))
+
+    assert MapSet.size(new_set) == ___
+  end
+
+  koan "I want my set in a list" do
+    assert MapSet.to_list(@set) == ___
+  end
+end