Migrated tests to jest

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

test2/fibonacci/fibonacci.js

@@ -0,0 +1,6 @@
+const fibonacci = n =>
+Array.from({ length: n }).reduce(
+(acc, val, i) => acc.concat(i > 1 ? acc[i - 1] + acc[i - 2] : i),
+[]
+);
+module.exports = fibonacci;