Add EIM holding page

This in order to explain to users where the Employment Income manual has gone
Add some style to EIM holding page
Swapped out some values for sass variables

You can find all of these defined here: https://github.com/alphagov/govuk_frontend_toolkit/tree/master/stylesheets. They're really useful <:^]
Removed superfluous div, reworded message.

That div didn't need to be there so I yanked it.
I also reworded the message a bit so the link doesn't have to be in brackets.
Redirect to EIM holding page for sections
Change stubbed HMRC manual

With the redirection of the EIM to a holding page, the HMRC related
tests were broken. This commit changes the manual to have different
stubbed data which doesn't clash.
Remove EIM JSON
Merge pull request #85 from alphagov/feature/employment-income-manual-holding-page

Employment income manual holding page