Iframe Support

[benash]

I'd love it if we could get Iframe support working. When I add an iframe tag directly to the markdown, the src attribute seems to be stripped out, as if I had just added <iframe> </iframe>

What do you think of this addition? If this is desirable, I'd be happy to work on it.

[benash]

My use case here is embedding Google Docs. Since we can't upload files, I thought a good solution would involve uploading files to Google Drive and then linking or embedding the docs on the wiki.