function isArrayOfStrings(arg) {
        var result = false;
        /* istanbul ignore else */
        if(Array.isArray(arg)) {
            result = (arg.filter(function(item){return typeof item !== 'string';}).length === 0);
        }
        return result;
    }
Returns true if the arg is an array of strings
@param {*} arg - the item to test
@returns {boolean} True if arg is an array of strings