Log Message:
Update ruby-sequel to 4.27.0.

=== 4.27.0 (2015-10-01)

* Don't stub Sequel.synchronize on MRI (YorickPeterse) (#1083)

* Make bin/sequel warn if given arguments that it doesn't use (jeremyevans)

* Fix the order of referenced composite keys returned by \ 
Database#foreign_key_list on PostgreSQL (jeremyevans) (#1081)

* Recognize another disconnect error in the jdbc/postgresql adapter (jeremyevans)

* In the active model plugin, make Model#persisted? return false if the \ 
transaction used for creation is rolled back (jeremyevans) (#1076)

* Use primary_key :keep_order option in the schema dumper if the auto \ 
incrementing column is not the first column in the table (jeremyevans)

* Set :auto_increment option correctly in the schema parser when the auto \ 
incrementing column is not the first column in the table (jeremyevans)

* Support :keep_order option to primary_key in schema generator, to not \ 
automatically make the primary key the first column (jeremyevans)

* Add new jsonb/json functions and operators supported in PostgreSQL 9.5+ \ 
(jeremyevans)

* Add before_after_save plugin, for refreshing created objects and resetting \ 
modified flag before calling after_create/update/save hooks (jeremyevans)

* Add Dataset#single_record! and #single_value! which don't require cloning the \ 
receiver (jeremyevans)

* Dataset#with_sql_single_value now works correctly for model datasets (jeremyevans)

* Optimize Dataset#single_value and #with_sql_single_value to not create an \ 
unnecessary array (jeremyevans)

* Make postgres adapter work with postgres-pr 0.7.0 (jeremyevans) (#1074)