Run casperjs tests with gulp

gulpfile.coffee

gulp.task "test", ->
  server = require('./server/server.coffee').listen 9002

  new Promise (resolve, reject) ->
    test = spawn 'casperjs', ['test', './test'],
      stdio: 'inherit'

    test.on 'close', (code) ->
      server.close()
      return reject(new Error("Tests failed")) unless code is 0
      resolve()