Relative dates start past incomplete periods

When requesting a relative date range using 'delta' and 'date' (or now if none), we should return the first complete period rather than a partial one.
Adding unit tests for when on period boundary

We need assurance that the code which shifts relative date ranges to start at the beginning of a complete period does not shift dates which are already at the start of a complete period.
Renaming confusing test names
Improving testing for when absent 'date' parameter

The tests were too complicated and their names were unclear. We now only have one test which just checks what it needs to in order to test the functionality.
Merge pull request #225 from alphagov/move-past-incomplete-periods

Move past incomplete periods
set replicaSet to be production
Change to MongoReplicaSetClient with multiple hosts

- Replace lots of instances of `'localhost'` with `['localhost']`
- Lots of tests hard code this: TODO - change to respect the app.config?
Merge pull request #227 from alphagov/really_reliable_replicated_replicas

Really reliable replicated replicas
Get replicaSet using os.getenv()

- Previously we assumed all environments would have a replicaset called 'production'
- This broke ci-new when it attemped to attach to a different set
- Adding in the variable allows us to override the value of the replicaset in various jenkins jobs
Merge pull request #229 from alphagov/replica_set_as_variable

Get replicaSet using os.getenv()