Create a method to clear terminal content

[rafaelcamargo]

Something like:

demo.openApp('terminal')
  .comand('node ./demo')
  .respond('Hello World!', { onCompleteDelay: 2000 })
  .clear()
  .end();

More info: #47 (comment)

[pfreitag]

+1 it would also be good if you could clear the editor