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
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.
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
Remove another assignment on ActiveRecord

- This would again complain about whitelisted parameters, when I tried
  to run the rails console.
Require 'rspec/expectations' and 'rspec/mocks' in spec_helper.rb
Remove deprecated specifying of which error is being raised