Support for grunt tasks and compiled templates

I got started on adding a template compiler and ended up having to redo `Gruntfile.js`.

* Copied in Gruntfile.js/_package.json from generator-webapp (gruntfile in project was for grunt0.3)
* Removed RequireJS ([ember.js has trouble w/ async loaders](https://github.com/emberjs/ember.js/issues/2194)). Will open another issue to address.
* Added pre-compiling of handlebars templates with [grunt-ember-templates](https://github.com/dgeb/grunt-ember-templates)
* Moved application & index templates into separate files
* Renamed `js` and `css` folders to `scripts` and `styles` for consistency when using sass/coffeescript
* ember:all now adds css with appendStyles
* Switched handlebars.js to handlebars.runtime.js
* Updated readme to include npm install & grunt server

2 Questions:

1. I'm not clear on what tests to write to accompany these changes. I added the new file checks. Any guidance?

2. I named the templates folder `/hbs` instead of `/templates` 
in the project to avoid confusion. They ultimately get put into a `/templates`
folder after running ember:all. Does this make sense or is it confusing?

    `generator-ember/templates`

        /hbs        # Handlebars templates
        /scripts    # Scripts
        /styles     # Styles

    Generates:

        /app
            /scripts
            /styles
            /templates