{VISUAL} doesn't keep the indentation

I have the following snippet:

```
snippet b block
    ${1}
        {VISUAL}
    end
```

And I have the following Ruby code

``` rb
class Foo
end
```

and I visually select those 2 lines, press `<Tab>b<Tab>`, then I expect to end up with this:

``` rb
*cursor*
  class Foo
  end
end
```

But I end up with this:

``` rb
*cursor*
  class Foo
end
end
```
