Use asset-url less helpers in stylesheets

So we get digested URLs in prod, and the corresponding long cache times.
Merge pull request #160 from alphagov/css_asset_paths

Use asset-url less helpers in stylesheets
Handle non-specific HTTP errors in Panopticon

Make sure we handle 422 and other such errors when registering with Panopticon.
Merge pull request #161 from alphagov/handle-panopticon-http-errors

Handle non-specific HTTP errors in Panopticon
Bump logstasher to 0.4.8

To get https://github.com/shadabahmed/logstasher/pull/20
Update govuk_content_models to 7.1.0

This gem in this app needs to be kept in lockstep with govuk_content_api
and panopticon or else the hydration process will break.
Merge pull request #162 from alphagov/bump-content-models-to-710

Update govuk_content_models to 7.1.0
Merge pull request #163 from alphagov/bump_logstasher

Bump logstasher to 0.4.8
Bump govuk_content_models to 7.1.1
Destroy all `SpecialistDocumentEditions`

These are no longer stored in the `editions` collection, so just remove
them completely.
Merge pull request #164 from alphagov/govuk-content-models-711

Fix up erroneous SpecialistDocumentEdition artefacts
Add airbrake

To send exceptions to errbit
Bump Rails to 3.2.17

To pick up recent security fixes
Merge pull request #166 from alphagov/bump_rails

Bump Rails to 3.2.17
Merge pull request #165 from alphagov/add_airbrake

Add airbrake
Add Jenkins branch build script
Merge pull request #167 from alphagov/branch_builds

Add Jenkins branch build script
Remove spurious action_mailer ses config.

This is overwritten by mailer.rb on deploy, but it's presence here will
only cause confusion.
Merge pull request #168 from alphagov/cleanup_mailer_config

Remove spurious action_mailer ses config.
Remove exception_notifier.

Also remove ses gem.  Althopugh this app still sends email, it no longer
uses the SES HTTP API, and therefore no longer needs this gem.