Add ability to auto-create replica set

This really should only be done in dev environments -- typically a data recovery
would be done prior to fully enabling the replica set and adding the indexes.

However, for ease of use in dev and vagrant environments, we just want to have mongo
working from the get-go.
Add a delay option to mongo_initiate_replica_set

Since the replica set can take a while to set up, particularly if
adding secondary nodes to a populated database, add a optional
delay.

This makes it a bit easier to ensure that the replica is set up
before moving ahead in automated solutions.
Update README
Update CHANGELOG
Check for mongo connectivity before initiating RS

This script is typically run very close to the point that the mongo
db is 'preinitialised' and/or started.

Wait for up to 5 seconds for a successful admin connection before
trying to add the replica set.

This makes for a happy automatic salt setup, but is generally useful
start mongo after preconfiguring
Ship the mongodb.log to logstash

Just ship it for now, add filters later.
Merge pull request #3 from ministryofjustice/include_replica_set_initiate

Include replica set initiate