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:

```elixir
thing = Thing.new
  |>> Foo.spam_thing(foo)
  |>> Bar.ham_thing(bar)
  |>> Baz.eggs_thing(baz)
```

Interfacing with Erlang functions also conveniently becomes easier:

```elixir
workers = state.workers
  |>> :queue.filter(&(&1 != worker))
  |>> :queue.in(new_worker(state.supervisor))
```

The pipe-last operator is also affectionately known as
"pipe harder".