Generate pod components within components subdirectory.

This PR makes `ember g component x-foo --pod` generate within components sub directory, resulting in 

```
app/pods/components/x-foo/component.js
app/pods/components/x-foo/template.hbs
```
made possible with [ember-resolver/pull/61](https://github.com/stefanpenner/ember-resolver/pull/61)

Feel free to close this if `app/pods/x-foo/component.js` is the preferred default.