Use MongoClient or MongoReplicaSet client instead of Connection
Fix indentation error
Cast default connection port to int.

Also use lower name for default connection class
Use MongoReplicaSetClient only if replicaSet option is enabled
Fix failing tests and add some default connection parameters.
Merge pull request #185 from r4fek/feature/issue170

Add support for Replica Sets using MongoClient and MongoReplicaSetClient. Closes #170
Updated changelog and version number
Allow nonrel models to have cross-db fks to relational dbs