function validatePinchDistance() {
      if (options.pinchThreshold !== null) {
        return pinchDistance >= options.pinchThreshold;
      }
      return true;
    }
Checks the user has pinched far enough
@return Boolean if <code>pinchThreshold</code> has been set, return true if the threshold was met, else false.
If no threshold was set, then we return true.
@inner