Update Redcarpet and remove initial Launchy command

This is in relation to https://github.com/nesquena/gitdocs/issues/74

I've also included a 'fix' to allow gitdocs operation on headless boxes, as Launchy doesn't handle the nonexistence of available browsers well at all, causing an immediate crash. 
I wasn't able to figure out how to easily toggle the applicable "config.global.load_browser_on_startup" option prior to starting gitdocs up to properly disable this functionality.