Change getCurrentSlug to pass back more information
Change getCurrentSlug to pass back more information

- Previously if we had a URL that was e.g. `http://smartanswers.dev.gov.uk/overseas-passports/y/afghanistan/applying` `getCurrentSlug()` would return `"overseas-passports"`
- Now from that URL we will return `"overseas-passports/y/afghanistan/applying"`
- This is based on a conversation with @antimega about the actual usefulness of what we're capturing. With this level of fidelity we capture not only that someone clicked on a link inside the `overseas-passports` flow, but the point in the flow that they decided to change their answer.

aledelcueto/smart-answers,lutgendorff/smart-answers,tadast/smart-answers,alphagov/smart-answers,askl56/smart-answers,aledelcueto/smart-answers,tadast/smart-answers,aledelcueto/smart-answers,askl56/smart-answers,aledelcueto/smart-answers,tadast/smart-answers,alphagov/smart-answers,ministryofjustice/smart-answers,ministryofjustice/smart-answers,lutgendorff/smart-answers,askl56/smart-answers,lutgendorff/smart-answers,tadast/smart-answers,ministryofjustice/smart-answers,alphagov/smart-answers,askl56/smart-answers,stwalsh/smart-answers,stwalsh/smart-answers,stwalsh/smart-answers,stwalsh/smart-answers,alphagov/smart-answers,lutgendorff/smart-answers