fix some file extensions

Task/Classes/CoffeeScript/classes.coffee

@@ -0,0 +1,14 @@
+# Create a basic class
+class Rectangle
+  # Constructor that accepts one argument
+  constructor: (@width) ->
+
+  # An instance variable
+  length: 10
+
+  # A method
+  area: () ->
+    @width * @length
+
+# Instantiate the class using the new operator
+rect = new Rectangle 2