code: function(includePath, rewriter)
          {
              return function(path, headers)
              {
                  var hash = "";
                  // this is unpkg specific
                  if(headers["X-Content-Version"] != null) {
                      var parts = path.split("/");
                      var index = 0;
                      // check to make sure it doen't already have one
                      if(parts[index].indexOf("@") === 0) {
                          index = 1;
                      }
                      parts[index] += "@" + headers['X-Content-Version'];
                      path = parts.join("/");
                  }
                  return rewriter(path, headers);
              }
          }
docs: /* rewrite