html -> markdown -> html

I wanted to use this plugin to write emails with sublime text. But when I activate GhostText within a gmail compose box, I get html in Sublime, and I don't want to write my emails in html.

Would it be feasible to integrate GhostText with [pandoc](http://pandoc.org)? Necessary additions would be
- new setting "use_pandoc" defaults to false
- detect if source is html
- add `pandoc -f html -t markdown` filter between chrome and sublime
- add `pandoc -f markdown -t html` filter between sublime and chrome

pandoc is very fast, so I don't think speed is a major concern here. If you're interested in this addition, I can implement it and make a pull request. (If you can tell me where the filters should go, that would be very helpful)