Print public links to jobs in both RSpec and Cucumber tests

This patch adds the Sauce authorized link to the `Example` (in RSpec) and `Scenario` (in Cucumber) objects. It then prints them out in the standard output (and can be used for custom formatters elsewhere).

Requires the patch to Sauce Whisk in pull request 11 (https://github.com/saucelabs/sauce_whisk/pull/11).