Remove utils module

src/utils.js

-'use strict';
-
-var createError = require('create-error');
-
-exports.cast = function (data) {
-  return new this(data);
-};
-
-exports.NotFoundError = createError('NotFoundError');
-exports.QueuedError = createError('QueuedError');
-
-exports.isUnknownRecord = function (err) {
-  return err.type === 'unknown_record';
-};
-
-exports.isQueued = function (err) {
-  return err.type === 'queued';
-};
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