Allow custom H1 and body for error pages
Store AKA hosts in the database

This means we will record hits against AKA hostnames when they appear in the
logs from our CDN.

This has made the `has_aka` field on Host and the code for finding aka hosts in
Transition::Import::DnsDetails confusing, hopefully I can simplify that...
Relate canonical and aka hosts

This allows us to simplify the Host model and the code for fetching DNS
details.
Add lib to autoload

This fixes an undefined constant Transition::OffSiteRedirectChecker in
MappingsController when bulk adding in development.
Make spec deterministic in the face of array order
Helpful error on 404 from /mappings/find_global

Had to amend the test to decode the apostrophe which Rails made into an HTML
entity because it now considers the string to be not HTML-safe.
Merge pull request #238 from alphagov/add_lib_to_autoload

Add lib to autoload
Merge pull request #231 from alphagov/helpful_404_on_find_global

Helpful 404 on find global
Merge pull request #236 from alphagov/store_aka_hosts_in_database

Store AKA hosts in database/Show AKA hits