Add support for piping

[ecton]

In some languages, piping allows passing the result of the left hand side of the operator in as the first parameter of invoking the right hand side as a function call. E.g, foo.len() |> Int.max(5) would be equivalent to calling Int.max(foo.len(), 5).

Since Muse is too dynamic to support traditional extension approaches, this pattern will hopefully serve as a reasonable alternative.