Upgrade to Ruby 2.0

Add newrelic in dev
Upgrade yajl-ruby to 1.2.0
Merge pull request #150 from alphagov/ruby-2.0

Upgrade to Ruby 2.0
Reduce the verbosity of elasticsearch logging

This switches the elasticsearch logging from STDERR to Rails' logger.
This means that the logging level will be appropriate to the environment.

Errors in production were obscured by huge quantities of successful requests
which often have large bodies.
Merge pull request #152 from alphagov/reduce_verbose_elasticsearch_logging

Reduce the verbosity of elasticsearch logging
Fix pending spec for section.chapters with hidden codes
Fix i18n deprecation warning
Switch to errbit