Do minor optimisations to factorial function.

Author: trekhleb

src/algorithms/math/factorial/factorial.js

@@ -5,7 +5,7 @@
 export default function factorial(number) {
   let result = 1;
 
-  for (let i = 1; i <= number; i += 1) {
+  for (let i = 2; i <= number; i += 1) {
     result *= i;
   }