Archive, multitagging, cleanup

Cleaned up the current snippets for consistency and minor problems, added multiple tags to most of them, archived a few.

snippets/gcd.md

@@ -9,10 +9,11 @@ Otherwise, return the GCD of `y` and the remainder of the division `x/y`.
 ```js
 const gcd = (...arr) => {
   const _gcd = (x, y) => (!y ? x : gcd(y, x % y));
-  return [].concat(...arr).reduce((a, b) => _gcd(a, b));
+  return [...arr].reduce((a, b) => _gcd(a, b));
 };
 ```
 
 ```js
 gcd(8, 36); // 4
+gcd(...[12,8,32]); // 4
 ```