Switched CI to using v4 Casper
Switched CI to using v4 Casper

no issue

- some new GScan changes mean that CI now throws a warning when using v3
  Casper, which causes tests to fail
- we need to switch to v4 to get the tests to pass
- we can't put v4 Casper in `main` because it'll autodeploy and be
  unusable for anyone downloading until Ghost 4.0 is released

ErisDS/Ghost,e10/Ghost,bitjson/Ghost,TryGhost/Ghost,janvt/Ghost,TryGhost/Ghost,TryGhost/Ghost,ErisDS/Ghost,janvt/Ghost,ErisDS/Ghost,e10/Ghost,bitjson/Ghost