Remove references to EmptySubquery

Subqueries are not supported in 1.0
Documentation for errors
Add yardopts
Documentation for Batch
Don't default an integer option to `false`
Documentation for CqlRowSpecification
Full updated documentation for DataSet
Documentation for Metal::Deleter
Documentation for Metal::Incrementer and Metal::Inserter
DataSet fixes
Documentation for Keyspace

Also always use connection pool
Documentation for Metal::Row
Documentation for Metal::RowSpecification
Documentation for Metal::Statement
Documentation for Metal::Updater
Documentation for Writer, DataSet
Update new relic instrumentation
Documentation for AssociationCollection
Documentation for Record::Associations
Documentation for BelongsToAssociation