Creates a dir
@param dir
@param cb
function mkpath(dir, cb) {
  dir = path.normalize(dir);
  var segs = dir.split(path.sep);
  var made = "";
  async.eachSeries(
      segs,
      function(seg, cb) {
        if (made.length || !seg.length) {
          made += "/";
        }
        made += seg;
        fs.exists(made, function(exists) {
          if (!exists) {
            fs.mkdir(made, function(err) {
              if (err && err.code === "EEXIST") {
                err = null; 
              }
              cb(err);
            });
            return;
          }
          fs.stat(made, function(err, stat) {
            if (err) {
              cb(err);
            } else if (stat.isDirectory()) {
              cb(null);
            } else {
              cb(new Error("Cannot create " + made + " (in " + dir + ") because it exists and is not a directory", "ENOENT"));
            }
          });
        });
      },
      function(err) {
        cb(err);
      });
}