function validateSwipeDistance() {
      var valid = true;
      //If we made it past the min swipe distance..
      if (options.threshold !== null) {
        valid = distance >= options.threshold;
      }

      return valid;
    }
Checks the user has swipe far enough
@return Boolean if <code>threshold</code> has been set, return true if the threshold was met, else false.
If no threshold was set, then we return true.
@inner