code: function copy (source, target) {
      var defer = Q.defer()
      fs.createReadStream(source)
        .on('error', defer.reject.bind(defer))
        .pipe(fs.createWriteStream(target))
        .on('error', defer.reject.bind(defer))
        .on('finish', defer.fulfill.bind(defer))
  
      return defer.promise
    }
docs: Replacement for [q-io/fs#copy](http://documentup.com/kriskowal/q-io#copysource-target)
  @param source
  @param target