code: public String single(final CharSequence name, final String def)
          throws IOException {
          final String value;
          final Iterator<String> params = this.param(name).iterator();
          if (params.hasNext()) {
              value = params.next();
          } else {
              value = def;
          }
          return value;
      }
docs: Get single param or default.
  @param name Name of query param
  @param def Default, if not found
  @return Value of it
  @throws IOException if something fails reading parameters