Fix build failure when component has child component

I stumbled upon the error case when the `component` has *child* `component`.
Such case found in [example todo app](https://github.com/component/todo), whose structure looks like below:

```
├── client
│   ├── boot
│   │   ├── component.json
│   │   ├── index.js
│   │   └── style.css
│   ├── item
│   │   ├── component.json
│   │   └── index.js
│   └── item-view
│       ├── component.json
│       ├── index.js
│       ├── style.css
│       ├── template.html
│       └── template.js
├── component.json
```
and the root `component.json` looks like:
```
{
  "name": "todo",
  "description": "TodoMVC component example",
  "version": "0.0.1",
  "local": ["boot"],
  "paths": ["client"]
}
```

So I added the test case `support/with-child-component` and another check to `pkg.parent` condition to make the test pass.

Please take a look and merge it if possible ;)

Thanks.