fundon/co-ware — pull request #1 by coderhaoxin (2014-08-20 15:55:34+00:00)
Title: if error listener has exist, ignore default onerror

当自定义 `on('error')` 存在时, 忽略默认 `onerror`.

bug: 原版本中
```js
this.outputErrors = 'test' !== this.env;
```
永远为 `true`