Feature: Add TestCase#outline? for conditionals in hooks

In Before/After hooks I commonly have a need to type check using the class name. One change I had to make while refactoring for the `2.0.0.beta.2` was updating from the previous Ast classes to the new TestCase mappings for scenarios/outlines. Adding the predicate method `outline?` provides a quick way to check vs. doing type based conditionals.
thanks :)