Check SASS compiles as part of Jenkins test runner

* Running asset precompile will catch SASS syntactic/reference errors earlier.
* Use set -e, to immediately fail if any command fails,  rather than than relying
on a manual exit, as we're running more than one 'test' command, more robust.
Merge pull request #616 from alphagov/test-asset-precompile

Check SASS compiles as part of Jenkins test runner
Stop UKVI A/B test
Show tax disc beta to 50% of users
Rename tax disc test and cohorts

This effectively creates a new A/B test using the
new weightings.
Set the weights for each cohort
Bump govuk_frontend_toolkit for weighted tests
Merge pull request #618 from alphagov/increase-tax-disc-beta

Show tax disc beta A/B test to 50% of users
Call imminence directly for find_nearest searches.

This change takes content_api out of the path for finding nearest places from a
postcode, as part of preparations for the move to the new content store.

Previously frontend was calling MapIt to get lat/long for a postcode, then
passing that location to content_api which in turn called imminence to get the
nearest places. Imminence now has the ability to call MapIt, so this change
removes the MapIt call here and instead calls imminence with the postcode,
receiving a list of places.
Merge pull request #619 from alphagov/location_from_imminence

Call imminence directly for find_nearest searches.
Pass the debug parameter through to rummager

This parameter allows the ranking options to be changed; for example, it
allows use of best-bets to be turned off.  It's useful to be able to
make these modifications on the live search results to compare the final
ranking that would be produced, and to check if options like popularity
information help for particular searches.
Merge pull request #620 from alphagov/pass_debug_to_search

Pass the debug parameter through to rummager
Clear accidentally added stuff in templates
Merge pull request #621 from alphagov/clean-out-javascripts-templates

Clear accidentally added stuff in templates
Merge pull request #617 from alphagov/remove-ukvi-ab-test

Stop UKVI A/B test
Don't use margin + 100% width for campaign header

As this causes the page to be larger than the screen.
Merge pull request #622 from alphagov/fix-campaign-header-overflow

Don't use margin + 100% width for campaign header
Clean up styling of campaign page on mobile devices

• Content no longer loses it's margin when viewed between 900px - 1000px wide

• Cleaned up behaviour of header / org logo on smaller screens
	(now only tries to render them left / right on desktop)

• Margin applied to section#landing instead of article.campaign

• Leading header image is no longer full window width on small browsers

• Leading header image no longer gets really tall on small browsers

• Some css in _campaigns.scss was unscoped (eg .organisation), these are
  now scoped

• Remove #extra_links rules (no longer in use)
Merge pull request #623 from alphagov/clean-up-campaign-styling

Clean up styling of campaign page on mobile devices
Update debug information on search results

For people such as search analyists who need to be able to see positions
and slugs for links (without hovering) to let them do their job more
efficiently.