Log Message:
databases/ruby-sequel: update to 5.17.0

=== 5.17.0 (2019-02-01)

* Support skip_auto_validations instance method in auto_validations plugin
  (oldgreen, jeremyevans) (#1592)

* Support :preconnect_extensions Database option for loading extensions before
  :preconnect option (jeremyevans)

* Avoid usage of Proc.new with implicit block as ruby 2.7+ deprecates this
  behavior (jeremyevans)

* Allow Sequel[].as to be used for constructing aliases with eager_graph
  (e.g. Model.eager_graph(Sequel[:a].as(:b))) (jeremyevans) (#1588)