Change scrolly-checkbox style

Our user research showed some users found the checkboxes to be a bit of a fiddle on mobile and tablet, so we're making the touch area a bit bigger and adding a border to make it apparent where the touchable edges are.
Move inputs to inside labels

So that the whole thing is clickable, but the inputs inside the labels.
Merge pull request #129 from alphagov/clumsy-fingers

Clumsy fingers
Update Slimmer

Updating Slimmer to 5.0.0 gives us the Report a Problem link at the
bottom of the page.
Use default prechecked state on page load

Rather than always prechecking select boxes, use the prechecked state
from the metadata about an email signup currently pulled from finder-api.
Remove text-align:center from #wrapper

With that declaration, the text in the report a problem link was centre
aligned. This commit removes it to make the text left aligned.
Merge pull request #131 from alphagov/report-a-problem

Report a problem
Merge pull request #130 from alphagov/feature/uncheck-email-signups-by-default-unless-msa

Use default prechecked state on page load
Allow Beta message to be passed in

With some Finders, the default beta message doesn't quite work for us.
This commit allows the beta message to be passed in as an optional
arguement.