doesn't look like the update_at fields properly updates

[mathieujobin]

(byebug) x
#<Setting updated_at: 2017-05-07 21:16:18 UTC, created_at: 2017-05-07 21:16:18 UTC, oid: "planet:c9f62372-6346-4a7b-818b-253758fd9b20", data: {"rock"=>"abc", "paper"=>"ok"}, _id: "41b5a4ae9eb9829225876d89ba43407c", _rev: "1-3f674e78841f531e959aee8f322b2b1b", type: "Setting">
(byebug) x.save
true
(byebug) x
#<Setting updated_at: 2017-05-07 21:16:18 UTC, created_at: 2017-05-07 21:16:18 UTC, oid: "planet:c9f62372-6346-4a7b-818b-253758fd9b20", data: {"rock"=>"abc", "paper"=>"ok"}, _id: "41b5a4ae9eb9829225876d89ba43407c", _rev: "1-3f674e78841f531e959aee8f322b2b1b", type: "Setting">
(byebug) x.data["papexxxr"] = "ok"
"ok"
(byebug) x.save!
true
(byebug) x
#<Setting updated_at: 2017-05-07 21:16:18 UTC, created_at: 2017-05-07 21:16:18 UTC, oid: "planet:c9f62372-6346-4a7b-818b-253758fd9b20", data: {"rock"=>"abc", "paper"=>"ok", "papexxxr"=>"ok"}, _id: "41b5a4ae9eb9829225876d89ba43407c", _rev: "1-3f674e78841f531e959aee8f322b2b1b", type: "Setting">
(byebug) 

model is as follow

require 'couchrest_model'

class Setting < CouchRest::Model::Base
  use_database "foo"
  timestamps!
  property :oid, String
  property :data, ActiveSupport::HashWithIndifferentAccess
  validates_presence_of :oid, :data

  design do
    view :by_oid
  end
end