Tests for awaitOption, chunk, chunkBy, and terminated

This PR adds simple tests for `awaitOption`, `chunk`, `chunkBy`, and `terminated`. It also uses scaladoc's syntax for multiline code blocks for code examples in docstrings. Otherwise scaladoc renders this

    Process(1,2,3,4) |> reduce(_ + _) == Process(10)
    Process(1) |> reduce(_ + _) == Process(1)
    Process() |> reduce(_ + _) == Process()

as

    Process(1,2,3,4) |> reduce(_ + _) == Process(10) Process(1) |> reduce(_ + _) == Process(1) Process() |> reduce(_ + _) == Process()