Update title for maternity-paternity calculator
Update maternity-paternity front page content

Content changes to meta and body, with splitting out of content to
devolved_body. This is mainly to follow on from public feedback on how
the smart answer is used.
The notice of leave deadline is always a Saturday

The "end of the week" is always classed as a Saturday. Make sure to
forward that many number of days once we've worked out the difference
calculation that we require.
Move specific integration test to end of file
Scope £4000 tests within maternity block

These responses will be used as an example for multiple edge cases
provided by the content designers. Rather than having a 'should' block
at the top-level for the parent response, keep these self-contained so
that the assertions are easier to read.
Adjust maternity/paternity leave end date by subtracting one

This date calculation was being too generous and providing an extra
day of leave. This is not what the policy stipulates.
Fix cases where pay end date was off by one
Fix calculation for notice request pay date

Don't use an attr_reader for the variable, instead reference the
instance variable, removing the code smell from the initialize.

Provided some extra test cases found by the content team.
Remove 'on or' copy statement
Copy changes to Statutory Maternity Pay result
Update copy for date leave hint
Call the method directly instead of using Object.send
Provide generic DateHelper module containing next_saturday method

This is the start of the work to reduce the duplication of the
next_saturday code that currently exists.
Merge pull request #189 from alphagov/maternity-paternity-content-and-calculator-fixes

Maternity paternity content and calculator fixes