feat (Modal) add support for the animations parameters in the modal.show API
chore (tests Modal) add test cases for the animation parameter in the modal.show API (only fade is supported)
feat (Screen) add test cases for steroids.screen.capture with the new output parameter
Merge pull request #139 from pentateu/topic/fade_modals_tests

Suppor for fade modals and PNG image output on screen.capture()