Add a pipe-last operator (|>>)

Because idiomatic Elixir interfaces are noun-first, it's too awkward
to use the pipe operator to build up a "thing" when your builder
functions are located in different modules. Functions where the
accumulated "thing" is the last argument of your functions
especially benefit from the pipe-last operator.

Example:

    thing = Thing.new
      |>> Foo.spam_thing(foo)
      |>> Bar.ham_thing(bar)
      |>> Baz.eggs_thing(baz)

Interfacing with Erlang functions also conveniently becomes easier:

    workers = state.workers
      |>> :queue.filter(&(&1 != worker))
      |>> :queue.in(new_worker(state.supervisor))

The pipe-last operator is also affectionately known as
"pipe harder".