v4.0.0

• Drop support for Ruby 1.8.7.
• Add tau and alpha as parameters to catchup algorithm.
• Record which algorithm was used to select a prompt.
• Add similar choice method to find similar (currently only identical) choices.
• Retry transaction when creating appearance if get deadlocked.

v3.2.1

• Create transaction and lock when creating a new appearance.
• Remove votes from vote CSV file that have NA for Appearance ID.
• Alter response for all_object_info_totals_by_date to be valid XML.

v3.2.0

• Save CSV exports to a database table instead of redis.

v3.1.0

• handle votes or skips that happen after an expired session
• don't allow votes / skips on appearances if their session ids don't match

v3.0.3

• use ActiveRecord quoting for table, column names
• add appearance id to votes and nonvote csv
• update cache hit/miss counters to use utc
• optimize objects_by_session_id
• disable catchup on surveys with more than 999 active choices