Format student finance scenarios in new format

We now include parse scnenarios via Smartdown
and don't rely on YML structure.
We also indicate question grouping with hyphens.
Update animal example simple example with scenarios

Make animal example simple identical in fixtures, lib and smartdown gem.
Add scenarios going through the different ways of going through
the question.
Fix broken plugin in animal example multiple

Date parsing is now done as part of the smartdown answer.
Date.parse would fail on Smartdown::Model::Answer::Date object.
Remove unused outcome from student finance forms flow
Test scenarios for animal example multiple
Tests to run through all scenarios

For every smartdown flow, this runs through all
the scenarios defined for them and:
- checks each set of questions has been asked in the right order
- checks the right outcome has been reached given the answers

Document the scenario checking rake task
Landlord immigration check: fix scenario parsing
Remove old rake task from jenkins build
Correct syntax of test fixture scenarios
Merge pull request #1211 from alphagov/scenarios-testing

Scenarios testing