RUBY-574 avoid doing special queries all the time
RUBY-568 Change to max message and max bson size setters
minor: adding file check to gem signing
RUBY-573 ShardingPoolManager seeds format fix and cursor pool handling
RUBY-572 fixing call to checkout_reader in DB#authenticate

The interface for MongoReplicaSetClient#checkout_reader was changed recently in RUBY-475. This usage of checkout_reader was missed and currently calls to DB#authenticate raise an exception.
clean-up: out-dated, we're not running them and auxiliary is misspelled \o/
RUBY-572 adding auth tests for replica sets and sharded clusters
RUBY-577 adding support in db#add_user for delegated credentials

This is new in MongoDB 2.4:
http://docs.mongodb.org/manual/reference/privilege-documents/#delegated-credentials

I've updated docs and preserved the old interface.