2.2.3

[core] Allow .assert.empty on FocusOption
[core] Allow .assert.defined on FocusOption
[selenium] WebDriver .executeJsOrThrow now accepts args and returns a result
[selenium] Add .parent as an extension to WebElement
[dom-zipper] Add .parent to move to the focus' parent
[dom-zipper] Allow .child() as shorthand for .child(1 of 1)
[ext-cats] Upgrade Cats to 1.4.0
[ext-scalaz] Upgrade Scalaz to 7.2.26
[ext-scalajs-react] Upgrade scalajs-react to 1.3.0