Implement metadata component

- Bump slimmer to a version with shared templates
- Remove bespoke metadata Sass
- Use shared template partial for metadata
- Update test to ensure shared metadata element it used
Show summaries on results for Drug Safety Alerts
Merge pull request #66 from alphagov/add-summary-to-results

Show summaries on results for Drug Safety Alerts
Merge pull request #67 from alphagov/govuk-components

Implement metadata component
Make result count show for keyword only searches

Add keyword presence into the boolean any_filters_applied?
Merge pull request #68 from alphagov/fix-no-results-keyword-buglet

Make result count show for keyword only searches
Make keywords show up in search results

Before, the search summary didn't show up keywords. This commit adds keywords to the summary and adds tests.
Add Airbrake
Merge pull request #71 from alphagov/airbrake

Add Airbrake
Reword tests
Merge pull request #70 from alphagov/add-sentence

Make keywords show up in search results