Update admin gem to 1.0.0
Replace silent margin classes with mixins

* Mixins aren’t using !important
* Generated CSS is cleaner
* Silent classes have been removed from admin gem
Explicitly pad list group items on site dashboard

* Before the default Bootstrap styles were being modified
* Instead use new admin gem helper class
Force link styles in filters to inherit colour

* Increased specificity of visited link styles in admin gem caused
filter options to go blue, prevent this from happening again
Use single quotes instead of double quotes

- This makes the airbrake gem line consistent with all of the others - I
  found this when looking through to upgrade Rails to v4.x and there was
  no reason for it to be quoted differently.
Merge pull request #321 from alphagov/use_single_quotes_in_gemfile

Use single quotes instead of double quotes
Remove the global_http_status column

- This is the third and final part of using type instead of http_status
  globally.
- I got a collation diff - I've `git add -p` only the parts of my
  db/structure.sql file relevant to adding this new migration.
Make breadcrumbs and titles consistent
Follow our style for string quoting
Merge pull request #322 from alphagov/tidy_up_titles

Tidy up titles/breadcrumbs
Remove redundant relationship

The next line defines a short name for the same relationship. We only use the
short version because nobody likes extra typing.
Merge pull request #323 from alphagov/remove_redundant_relationship

Remove redundant relationship
Bump .ruby-version to 2.1.2
Merge pull request #319 from alphagov/remove_global_http_status_column

Remove the global_http_status column
Change the remove_global_http_status_column migration to be reversible

- Following me making this only a `change` migration in #319, a discussion
  happened in which it was decided that it is important that it is
  reversible, otherwise things break in the event of an aborted deploy
  if the column removed does not rollback to exist again.
Merge pull request #317 from alphagov/upgrade-admin-gem

Upgrade admin gem to 1.0.0
Merge pull request #325 from alphagov/make_global_http_status_removal_migration_reversible

Change the remove_global_http_status_column migration to be reversible
Update type validation specs

Two tests using ensure_validation_of were still passing even though they
didn't have 'unresolved' in the array which should match the supported
types of mappings. Since they continue to pass as long as all elements
of the array the matcher receives are valid (even if the array is empty),
I think the clearest thing to do here is to just pass it Mapping::SUPPORTED_TYPES.
Merge pull request #326 from alphagov/update_validate_inclusion_specs

Update type validation specs
Merge pull request #324 from alphagov/upgrade-ruby-to-2.1.2

Bump .ruby-version to 2.1.2