add coffeescript demo

coffeescripts/test.coffee

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+# Assignment:
+number   = 42
+opposite = true
+
+# Conditions:
+number = -42 if opposite
+
+# Functions:
+square = (x) -> x * x
+
+# Arrays:
+list = [1, 2, 3, 4, 5]
+
+# Objects:
+math =
+  root:   Math.sqrt
+  square: square
+  cube:   (x) -> x * square x
+
+# Splats:
+race = (winner, runners...) ->
+  print winner, runners
+
+# Existence:
+alert "I knew it!" if elvis?
+
+# Array comprehensions:
+cubes = (math.cube num for num in list)