Improve code quality and write tests

node_modules/has-symbols/index.js

@@ -0,0 +1,13 @@
+'use strict';
+
+var origSymbol = global.Symbol;
+var hasSymbolSham = require('./shams');
+
+module.exports = function hasNativeSymbols() {
+	if (typeof origSymbol !== 'function') { return false; }
+	if (typeof Symbol !== 'function') { return false; }
+	if (typeof origSymbol('foo') !== 'symbol') { return false; }
+	if (typeof Symbol('bar') !== 'symbol') { return false; }
+
+	return hasSymbolSham();
+};