Update Fibonacci solution, test to focus on arrays

Previous Fibonacci solution didn't use arrays, and since this is an
array-heavy section, it seemed better to have that be the method here.

Also, it accounts for entering 0 as an argument without having to add
any extra code, which takes care of some currently open issues.
Issues #192 and #236 are about the same thing.

I added a test for that as well.

10_fibonacci/solution/fibonacci-solution.js

@@ -1,14 +1,10 @@
 const fibonacci = function(count) {
-  if (count < 0) return "OOPS";
-  if (count === 0) return 0;
-  let a = 0;
-  let b = 1;
-  for (let i = 1; i < count; i++) {
-    const temp = b;
-    b = a + b;
-    a = temp;
+	if (count < 0) return "OOPS"
+	const fibPart = [0, 1];
+	for (let index = 1; index < count; index++) {
+		fibPart.push(fibPart[index] + fibPart[index -1]);
 	}
-  return b;
+	return fibPart[count];
 };
 
 module.exports = fibonacci;

10_fibonacci/solution/fibonacci-solution.spec.js

@@ -16,6 +16,9 @@ describe('fibonacci', () => {
   test('25th fibonacci number is 75025', () => {
     expect(fibonacci(25)).toBe(75025);
   });
+  test('0th fibonacci number is o', () => {
+    expect(fibonacci(0)).toBe(0);
+  });
   test("doesn't accept negatives", () => {
     expect(fibonacci(-25)).toBe('OOPS');
   });