Add tasks for all the new languages

Task/Sierpinski-triangle/Elm/sierpinski-triangle.elm

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+import String exposing (..)
+import Html exposing (..)
+import Html.Attributes as A exposing (..)
+import Html.Events exposing (..)
+import Html.App exposing (beginnerProgram)
+import Result exposing (..)
+
+sierpinski : Int -> List String
+sierpinski n =
+  let down n = sierpinski (n - 1)
+      space n = repeat (2 ^ (n - 1)) " "
+  in case n of
+       0 -> ["*"]
+       _ ->    List.map ((\st -> space n ++ st) << (\st -> st ++ space n)) (down n)
+            ++ List.map (join " " << List.repeat 2) (down n)
+
+main = beginnerProgram { model = "4", view = view, update = update }
+
+update newStr oldStr = newStr
+
+view : String -> Html String
+view levelString =
+  div []
+    ([ Html.form
+          []
+          [ label [ myStyle ] [ text "Level: "]
+          , input
+            [ placeholder "triangle level."
+            , value levelString
+            , on "input" targetValue
+            , type' "number"
+            , A.min "0"
+            , myStyle
+            ]
+            []
+          ]
+     ] ++
+     [ pre [] (levelString
+               |> toInt
+               |> withDefault 0
+               |> sierpinski
+               |> List.map (\s -> div [] [text s]))
+     ])
+
+myStyle : Attribute msg
+myStyle =
+  style
+    [ ("height", "20px")
+    , ("padding", "5px 0 0 5px")
+    , ("font-size", "1em")
+    , ("text-align", "left")
+    ]