code: function(config, stream, extras, callback) {
      stream = stream.pipe(through.obj(function(file, enc, cb) {
  
        var contents = file.contents.toString();
        var changed = false;
  
        if(file.prev) {
          changed = true;
          file.prev.$el = file.prev.$el || cheerio.load(file.prev.contents.toString());
          var title = file.prev.$el('h1').first().text();
          contents = contents.replace(/MBINSERTPREVLABEL/g, title);
          var href = path.relative(path.dirname(file.relative), file.prev.relative);
          contents = contents.replace(/MBINSERTPREVHREF/g, href);
        }
  
        if(file.next) {
          changed = true;
          file.next.$el = file.next.$el || cheerio.load(file.next.contents.toString());
          var title = file.next.$el('h1').first().text();
          contents = contents.replace(/MBINSERTNEXTLABEL/g, title);
          var href = path.relative(path.dirname(file.relative), file.next.relative);
          contents = contents.replace(/MBINSERTNEXTHREF/g, href);
        }
  
        if(changed) {
          file.contents = new Buffer(contents);
          file.$el = undefined;
        }
  
        cb(null, file);
  
      }));
      callback(null, config, stream, extras);
    }
docs: Pipe through all the files and insert the title and link instead of the placeholders.