content sorting enhances

prepend sorting of contents by `ref_no`
Merge pull request #98 from bitzesty/content-sorting-enhances

content sorting enhances
Bump paper_trail gem.

Version 3.0.3 has been yanked, and is failing to install if not already
present.
Merge pull request #100 from alphagov/fix_paper_trail

Bump paper_trail gem.
Remove lrucache.

It's no longer used since needs are stored locally.
Use memcached instead of in-process cache

memcached is installed on all the app servers, so it makes sense to use
it.  This will reduce the memory usage of the Rails workers, and allow
workers on a given server to share the cache.
Remove unicorn config overrides.

This means that it will use the same defaults as most of the other apps.
Specifically, this will reduce the number of workers to 2 per box in
line with the other publishing app.  This should relieve some of the
memory pressure on the backend servers.
Merge pull request #99 from alphagov/remove_unicorn_config

Remove unicorn config overrides.
Merge pull request #101 from alphagov/reduce_memory_usage

Use memcached instead of in-process cache