= New Features

* The date_arithmetic extension now supports arbitrary expressions
  as interval values on PostgreSQL 9.4+.  Previously, only integers
  were supported for the interval values.

= Other Improvements

* Most Kernel#respond_to? calls have been converted to equivalent
  defined? calls for better performance.  defined? is a keyword
  and is about 50% faster for the same behavior.

* The is_distinct_from extension now supports the IS DISTINCT FROM
  syntax natively on SQLite 3.39+, instead of emulating it.

* HAVING without GROUP BY is now supported on SQLite 3.39+.

* Coverage testing has been significantly expanded.  Previously,
  the core, model, plugin, and extension code had 100% line/branch
  coverage.  100% line/branch coverage has been added for the
  core extensions, bin/sequel, and the postgres adapter with the
  pg driver.
