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
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
Merge pull request #319 from alphagov/remove_global_http_status_column

Remove the global_http_status column
Merge pull request #317 from alphagov/upgrade-admin-gem

Upgrade admin gem to 1.0.0
Update all of the gems so that Rails 4 works

- I've probably missed some, but there'll be further updates as I go
  through every error that now exists.
- Updating RSpec to 3.0.1 removes `its` - luckily there's an rspec-its
  gem that ports the 2.x behaviour to 3.
Fix some errors that came before any red tests

- Not entirely sure what these change, but I've done what the error
  output told me to do to fix the error:

  - Eager load the application only in production.
  - Remove the mass-assignment protection and the whitelist attributes
    ActiveRecord setting - this is done by strong_parameters in Rails 4.
Using match for routes is deprecated - use get for the error pages
Make RSpec render_views work again by including a new config line