Controller Generator

Simple generator for single controllers.

`mix phoenix.gen.controller controller_name`

generates

```
web/controllers/controller_name_controller.ex
web/views/controller_name_view.ex
web/templates/controller_name/
```

The generator would assume its a "resource" and add empty implementations.

When complete it would output to the console an example router code `resource "/controller_name", MyApp.ControllerName` so the user can copy/paste it into the router file.

Potential issues/Questions:
- I may need them to pass in the application name.

@josevalim @chrismccord lemme know what ya'll think. I think this is maybe step one for scaffolding, once we get ecto we can improve it even more.