Support for clipboard content other than text?

I discovered `dot-clipboard` yesterday and am really excited about it.

It seems like the `data` object is always a plaintext string, even if the content copied was HTML. In this codebase I see other types like `html` and `png`, but I know nothing about AppKit / Objective C so I'm a bit lost. Are those types supported by `clipboard-watcher`?

``` js
if(type === 'html'){
return [$.NSHTMLPboardType, 's'];
}

if(type === 'png'){
return [$.NSHTMLPboardType, 'i'];
}

if(type === 'text'){
return [$.NSStringPboardType, 's'];
}
```