Remove Number type coercion.

index.js

@@ -1,7 +1,6 @@
 'use strict';
 
-module.exports = function isNegativeZero(value) {
-	var number = Number(value);
+module.exports = function isNegativeZero(number) {
 	return number === 0 && (1 / number) === -Infinity;
 };
 

test.js

@@ -21,12 +21,6 @@ test('not negative zero', function (t) {
 	t.end();
 });
 
-test('things whose valueOf is negative zero', function (t) {
-	t.ok(isNegativeZero({ valueOf: function () { return -0; } }), 'object with valueOf of negative zero is negative zero');
-	t.ok(isNegativeZero('-0'), 'string negative zero is negative zero');
-	t.end();
-});
-
 test('negative zero', function (t) {
 	t.ok(isNegativeZero(-0), 'negative zero is negative zero');
 	t.end();