Create v2 of calculate-statutory-sick-pay

This is based on the v1 at cb62cb8.
Create a copy of the flow's content for V2
Add an integration test showing a completed SSP calculation

This gets us nearer to an example output page for where we'll hook in
the assertions for the weekly calculated output.
Move initialize to top of class
Produce weekly SSP dates and rates using SSP calculator

Generate all of the information required to show the weekly payments
to users given the sick date period.
Produce a markdown formatted list of the SSP weekly dates and rates
Hook up formatted_sick_pay_weekly_dates_and_rates to outcome

Use the formatted response (markdown table) instead of the raw Ruby
object.
calculate the weekly rates rather than precalculating it
Refer to v2 of the calculator YML
Weekly rates should always should the _end_ of the week

In this case, that means Saturday.
Work out the payable amounts per week from the SSP payment total

There are cases where the total will be smaller than the number of
weeks off depending on the user's case. To deal with this, deduct the
weekly (calculated) rate from the total until we hit zero so we know
overpayment doesn't occur.
Supply formatted_sick_pay_weekly_amounts for the tabular data