Deprecate placeholder classes

@AlbertoElias:

```js
// doubling the var keyword: everything looks aligned
// and is easy to move around
var foo = 'bar';
var bar = 'baz';

// One var keyword only:
// not aligned with tabs
// reordering 1st or last lines requires changes
var foo = 'bar',
	bar = 'baz';
```

So doubling `var` statements win.

Does that make sense?