add casperjs as a developer dependency
add casperjs as a developer dependency

saulirajala/wraith,peruukki/wraith,BBC-News/wraith,BBC-News/wraith,LessonPlanet/wraith,saulirajala/wraith,peruukki/wraith,BBC-News/wraith,LessonPlanet/wraith,saulirajala/wraith,peruukki/wraith,LessonPlanet/wraith