Comments should not be stripped from 'import' statements and language pragmas

Consider:

``` haskell
module Foo where
import Data.Monoid -- from base
import Data.List -- from base
```

And then:

```
$ stylish-haskell /tmp/Foo.hs
module Foo where
import Data.List
import Data.Monoid
$
```

The comments shouldn't be stripped from the end, ideally. At the very least this is inconsistent with the default behavior which will preserve comments in most other positions.