specs for dataset#frequency
failing spec for: Quandl::Cassandra::Column::Write given tiny data array should have written the data
spec
insert_columns_in_batches_with_threads does not care how many rows are sent
add Quandl::Cassandra::Batch
refactor InsertColumns to use Batch class
add select_data_aasync
split Batch into subclasses. include Batch::Logging if flagged
InsertColumnAttributes uses Batch.insert
insert_in_batches without threads
Base::Connection methods use #with_connection
Merge branch 'develop'
Release 0.3.0.