Fixes issue #42
Also adds logic for private torrents requiring site tracker as the main tracker (otherwise there's no point on uploading them on the site)
Changes upload.html wording to reflect the requirement to have the tracker, not necessarily as the first one.
These changes add a macro that creates the relevant HTML markup for a
markdown editor. In the main.js file, we bind the relevant elements with
the marked library, so users can see their contents in a HTML format.