A couple of tabulate/Tabulators.groupBy examples

[Raab, Donald]

I updated our kata with the latest changes in the Dec. 17 binaries.  Since groupBy was removed in this release I had to work through Brian's new tabulate/Tabulator approach in a couple places.  Except for some type inference problems where I had to specify some extra types in various places it was not too hard to get to work.  Not sure if there is an easier solution for the types here.

A simple example.

Before:

	Map<String, Collection<Customer>> multimap = this.company.getCustomers().stream().groupBy(Customer::getCity);

After:

      Map<String, Collection<Customer>> multimap =
            this.company.getCustomers()
                .stream()
                .tabulate(Tabulators.<Customer, String>groupBy(Customer::getCity));


A more complex example.

Before:

        Map<Double, Collection<Customer>> multimap = this.company.getCustomers()
            .stream()
            .groupBy(customer ->
                customer.getOrders()
                    .stream()
                    .flatMap((Block<? super LineItem> sink, Order element) -> {element.getLineItems().forEach(sink);})
                    .map(LineItem::getValue)
                    .reduce(0.0, (x, y) -> Math.max(x,y)));

After:

        Map<Double, Collection<Customer>> multimap = this.company.getCustomers()
            .stream()
            .tabulate(Tabulators.<Customer, Double>groupBy((Customer customer) ->
                customer.getOrders()
                    .stream()
                    .<LineItem>flatMap((Block<? super LineItem> sink, Order element) -> {
                        element.getLineItems().forEach(sink);
                    })
                    .<Double>map(lineItem -> lineItem.getValue())
                    .reduce(0.0, (x, y) -> Math.max(x, y))));