F!! Printable scenario - to better support BDD

[emilybache]

I've added a new library class PrintableScenario, with an example test of how to use it, and made a start on the documentation.

One of the methods has a checked exception which seemed to affect another test - I'm not sure what to do about that.

Look forward to discussing this proposed change with Llewellyn - we have booked a meeting to do so soon.

[LarsEckart]

I think what you need is the following. These comments in the java file:

// begin-snippet: MySnippetName
public class PrintableScenarioTest
{
  @Test
  public void printBDDScenario() throws Exception
  {
    PrintableScenario story = new PrintableScenario("Buy Groceries", "Bob puts two items in the shopping cart");
    User currentUser = new User();
    ShoppingCart shoppingCart = new ShoppingCart(currentUser);
    story.given(new Printable<>(currentUser, UserPrinter::print),
        new Printable<>(shoppingCart, ShoppingCartPrinter::print));
    story.when("Add oranges to the cart", () -> {
      shoppingCart.add("Oranges", 1, BigDecimal.valueOf(5));
      return null;
    });
    story.when("Add apples to the cart", () -> {
      shoppingCart.add("Apples", 3, BigDecimal.valueOf(4));
      return null;
    });
    Approvals.verify(story.then());
  }
}
// end-snippet

and then you can reference it here in markdown with snippet: MySnippetName

[emilybache]

I just updated this PR following conversation with Llewellyn. I think he probably wants to change a few more things too.