function charsLeftThreshold(input, thereshold, maxlength) {
        var output = true;
        if (!options.alwaysShow && (maxlength - inputLength(input) > thereshold)) {
          output = false;
        }
        return output;
      }
Return true if the indicator should be showing up.

@param input
@param thereshold
@param maxlength
@return {number}