Accept teardown lambdas as callbacks for scenarios

[vishalkhanna1995]

Presently, one has to resort to placing the teardown code inside the last step for a scenario. It would be nice to accept that code as a lambda for the scenario method.

Example usage:

scenario("test opening homepage", () -> { tearDown(); }, given("browser is open", () -> { DriverHooks.setUp("Chrome_1024x768"); }));