added decrement solution and added mix skeleton

lib/decrement.js

@@ -2,8 +2,9 @@
  * Write a function that decrements the value of the first parameter
  * @param {Number} a
  */
-function decrement() {
+function decrement(a) {
   // write code here
+  return a - 1;
 }
 
 module.exports = decrement;

lib/index.js

@@ -15,6 +15,7 @@ module.exports = {
   max: require("./max"),
   median: require("./median"),
   min: require("./min"),
+  min: require('./mix'),
   permute: require("./permute"),
   power: require("./power"),
   prime: require("./prime"),

lib/mix.js

@@ -0,0 +1,7 @@
+// Write a function that returns the contents of an array in random order
+
+function mix(a) {
+//write code here
+}
+
+module.exports = mix;