renderer cannot handle whitespace trimming

Hi,

I tried following haml sentence, but it doesn't properly work:

```
%img
%pre><
  foo
  bar
%img
```

http://haml.info/docs/yardoc/file.REFERENCE.html#whitespace_removal__and_

I expected:

```
<img /><pre>foo
bar</pre><img />
```

but result is:

```
<img />
<pre>
  foo
  bar
</pre>
<img />
```

BTW, thanks, for useful haml alternative parser for Perl ;-)
