CoffeeScript preferred styles

Use `@` instead of `this` for scoping

Prefer double quotes to preserve interpolation, allow for more complex strings,  make selectors easier to read and for overall consistency.
* `$("[data-role='title']")` or `$("input[type='text']")`
* `"Isn't this nice?"`
* `"It is #{nice}"`
I agree with Joe. Instead of a broad rule like "use `@` anywhere you'd use `this`", I would prefer something more specific like "Prefer `@` over `this` for referencing instance properties". It honestly looks weird to me to see `@` standalone. I've seen this happen generally in two cases:

`$(@)` (for `$(this)`):

```coffee
$('.some_selector').on 'click', ->
  $(@).hide()
```

`@` as the final line of a method (for returning `this`):

```coffee
class Foo
  set: (properties) ->
    _.extend this, properties
    @
```

I have two reasons for using a more specific guideline:

1. Only using `@` for instance attributes and methods feels more like Ruby, so it's less of a context switch.
2. For a while it was actually discouraged and Jeremy Ashkenas [briefly considered][1] removing support for bare `@` in CoffeeScript ([discussion][2]). Perhaps a weak point, but ultimately nothing was done because of the controversy around it. ([It is removed][3] in the upcoming "CoffeeScriptRedux".)

[1]: https://twitter.com/jashkenas/status/111274571608489984
[2]: https://github.com/jashkenas/coffeescript/issues/1601#issuecomment-1794427
[3]: https://github.com/jashkenas/coffeescript/issues/1601#issuecomment-23527282