Reorganize existing app files into macOS folder

- Add an iOS target

Metaballs-iOS/ViewController.swift

@@ -0,0 +1,20 @@
+//
+//  ViewController.swift
+//  Metaballs-iOS
+//
+//  Created by Eryn Wells on 10/7/18.
+//  Copyright © 2018 Eryn Wells. All rights reserved.
+//
+
+import UIKit
+
+class ViewController: UIViewController {
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        // Do any additional setup after loading the view, typically from a nib.
+    }
+
+
+}
+