Log Message:
Update ruby-sequel to 4.38.0.

=== 4.38.0 (2016-09-01)

* Support :driver_options option when using the postgres adapter with pg driver \ 
(jeremyevans)

* Don't use after commit/rollback database hooks if the model instance methods \ 
are not overridden (jeremyevans)

* Add SQL::NumericMethods#coerce, allowing code such as Sequel.expr{1 - x} \ 
(jeremyevans)

* Support ** operator for exponentiation on expressions, similar to +, -, *, and \ 
/ (jeremyevans)

* Add Sequel::SQLTime.date= to set the date used for SQLTime instances (jeremyevans)