Introduce Pipeline (|>) Operator

[leandromoh]

Introduces a new operator |> similar to F#, OCaml, Elixir, Elm, Julia, Hack, Clojure, and LiveScript.

64 |> sqrt is equivalent to sqrt(64)

This allows for greater readability when chaining several functions together. For example, given the following functions:

string DoubleSay (string str) {
  return str + ", " + str;
}

string Capitalize (string str) {
  return char.ToUpper(str[0]) + str.Substring(1).ToLower();
}

string Exclaim (string str) {
  return str + '!';
}

...the following invocations are equivalent:

var result = Exclaim(Capitalize(DoubleSay("hello")));
result //=> "Hello, hello!"

var result = "hello"
  |> DoubleSay
  |> Capitalize
  |> Exclaim;

result //=> "Hello, hello!"

multiple argument functions

let newScore = "70"
  |> int.Parse
  |> (_ =>  3 + _ )
  |> (_ => BoundScore(0, 100, _));

// As opposed to: let newScore = BoundScore( 0, 100, int.Parse("70") + 3 )

underscore is not required; it's just a lambda function, so you can use any parameter name you like.

[HaloFour]

Duplicate of #74