function nthArg(n) {
      n = toInteger(n);
      return rest(function(args) {
        return baseNth(args, n);
      });
    }
Creates a function that returns its nth argument. If `n` is negative,
the nth argument from the end is returned.

@static
@memberOf _
@since 4.0.0
@category Util
@param {number} [n=0] The index of the argument to return.
@returns {Function} Returns the new function.
@example

var func = _.nthArg(1);
func('a', 'b', 'c', 'd');
// => 'b'

var func = _.nthArg(-2);
func('a', 'b', 'c', 'd');
// => 'c'