Order exercise folders

Ordered the exercise folders by placing their numbers in their folder name

08 calculator/calculator.js

@@ -0,0 +1,32 @@
+const add = function() {
+	
+};
+
+const subtract = function() {
+	
+};
+
+const sum = function() {
+	
+};
+
+const multiply = function() {
+
+};
+
+const power = function() {
+	
+};
+
+const factorial = function() {
+	
+};
+
+module.exports = {
+  add,
+  subtract,
+  sum,
+  multiply,
+  power,
+  factorial
+};