no longer require cassandra gem
connection updates
keep example of thrift options
fix up attribute_methods_generated
oops, undo checkin to persistence.rb
v4.7.1
remove batch_start, batch_end
remove leading whitespace
move errors require to lib file so that Base dependency does not exist
Take parts of pull request #26
use base_class implementation from active_record
a better exception message
also support if self == Base
implement schema actions: drop_column_family, alter_column_family, add_index, drop_index