Notifier command wants to run in app dir

The command the notifier is likely to want to run in the directory of
the currently deployed version.
Merge pull request #553 from alphagov/add-notifier-app

Notifier command wants to run in app dir
Add more context when no feature scenarios

When checking the results of a smokey run; if there are no features in a
scenario then provide a bit more context.
Merge pull request #554 from alphagov/smokey-feature-exception

Add more context when no feature scenarios
Update puppet-collectd commit hash

The branch has been rebased on upstream.
Set up postgres secondary

- Factor out postgres stuff into it's own module
- Set up streaming binary replication

Note that this does not cover getting the primary's database onto the
secondary and getting it up to speed.
Live clone of postgres database

This introduces a script that can be run on a new secondary to bring it
up to speed with a primary without having to take the primary down.

On the priamry the checkpoint_segments and wal_keep_segments have been
increased to allow the secondary to catch up on writes that happen
during it copying the data over.

A login user has been introduced on the primary as well, as that is
needed for the pg_basebackup command.

This is modified slightly from
http://www.rassoc.com/gregr/weblog/2013/02/16/zero-to-postgresql-streaming-replication-in-10-mins/

I've gnoe with syncing to a separate directory and then rsyncing to
preserve things like the certificate and recovery.conf
Set pp_postgres::server in primary/secondary def

The classes depend on pp_postgres::server so it should be explicit in
their definition.
Factor out a pp specific hba rule define

This wraps up some common defaults for the performance platform to both
reduce duplication and avoid the risk of bad configurations.
Remove redundant postgres code from performanceplatform

It has moved into the pp_postgres module.
Fix postgres start_replication.sh

@timmow noticed that this was not copying the base backup into the
correct place. Also, it was not failing when subcommands failed.
fix typo in postgres start_replication script