Remove crude shim for ES6 Set. #904

src/classes/ShimSet.coffee

@@ -1,18 +0,0 @@
-class ShimSet
-  constructor: ->
-    @elements = {}
-    @size = 0
-  has: (value) ->
-    value of @elements
-  add: (value) ->
-    return if @elements[value]
-    @elements[value] = true
-    @size++
-  delete: (value) ->
-    return unless @elements[value]
-    delete @elements[value]
-    @size--
-
-window.Set = ShimSet unless 'Set' of window
-
-return ShimSet