Migrated tests to jest

Used jest-codemods to migrate, will have to pass everything by hand before we can merge.

test/primes/primes.js

@@ -1,8 +0,0 @@
-const primes = num => {
-let arr = Array.from({ length: num - 1 }).map((x, i) => i + 2),
-sqroot = Math.floor(Math.sqrt(num)),
-numsTillSqroot = Array.from({ length: sqroot - 1 }).map((x, i) => i + 2);
-numsTillSqroot.forEach(x => (arr = arr.filter(y => y % x !== 0 || y === x)));
-return arr;
-};
-module.exports = primes;