Add support for $warn and $debug

[shawnwildermuth]

Would be nice if $warn and $debug would write to VS Output Window. I think:

$warn == Trace.WriteLine
$debug == Debug.WriteLine

Awesome if we could get this in the Browser's output window, but that's a significant effort, in VS's window is plenty for me.

[kogir]

If you're referring to Sass's @warn and @debug directives, I'll take a quick look and see how the Sass compiler implements them. Can't make any promises though.

[shawnwildermuth]

Yeah, I meant @warn/@debug. I talked with Paul via twitter and he asked me to add the issue. Thanks!