code: function uploadFile(file, request, host) {
    return function(cb) {
      request
        .post(host + '/file/' + file.hash)
        .attach('data', file.abs)
        .end(function(err, res) {
          if (err) return cb(err);
          if (res.error) return cb(res.error);
          return cb();
        });
    };
  }
docs: Upload a single file to the build server
  
  @param {String} file
  @param {Request} request
  @param {String} host
  @return {Function}