add the simplest possible hash replacement with tests

lib/virtual/list.rb

@@ -0,0 +1,47 @@
+class List
+
+  def initialize
+    @next = nil
+  end
+  def empty?
+    @next.nil?
+  end
+
+  def get(key)
+    if( @next )
+      return @next.get(key)
+    else
+      return nil
+    end
+  end
+
+  def set(key , value)
+    if(@next)
+      @next.set(key,value)
+    else
+      @next = Node.new(key,value)
+    end
+    value
+  end
+end
+
+class Node < List
+  def initialize(key,value)
+    @key = key
+    @value = value
+  end
+  def get(key)
+    if(@key == key)
+      return @value
+    else
+      return super(key)
+    end
+  end
+  def set(key,value)
+    if(@key == key)
+      @value = value
+    else
+      super(key,value)
+    end
+  end
+end