Allow nested components in separated files.

Eg :
```
src/component/
├── docs
│   ├── demo.html
│   ├── demo.js
│   └── readme.md
├── component.subcomponent.js
├── component.js
└── test
    └── component.spec.js
```

where `component.js` defines
```javascript
angular.module('lib.component', [])
//...
```
and `component.subcomponent.js` defines
```javascript
angular.module('lib.component.subcomponent', ['lib.component'])
//...
```