Conversion to Swift 5

- convert all targets to Swift 5
- bump .swift-version
- update podspec
- fix warnings

Example/AppDelegate.swift

@@ -28,7 +28,7 @@
     class AppDelegate: UIResponder, UIApplicationDelegate {
         var window: UIWindow?
         
-        func application(_ application: UIApplication, willFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey : Any]? = nil) -> Bool {
+        func application(_ application: UIApplication, willFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey : Any]? = nil) -> Bool {
             AppDelegate.setupArmchair()
             return true
         }

Example/Images.xcassets/AppIcon.appiconset/Contents.json

@@ -1,5 +1,15 @@
 {
   "images" : [
+    {
+      "idiom" : "iphone",
+      "size" : "20x20",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "iphone",
+      "size" : "20x20",
+      "scale" : "3x"
+    },
     {
       "idiom" : "iphone",
       "size" : "29x29",
@@ -30,6 +40,16 @@
       "size" : "60x60",
       "scale" : "3x"
     },
+    {
+      "idiom" : "ipad",
+      "size" : "20x20",
+      "scale" : "1x"
+    },
+    {
+      "idiom" : "ipad",
+      "size" : "20x20",
+      "scale" : "2x"
+    },
     {
       "idiom" : "ipad",
       "size" : "29x29",
@@ -59,6 +79,16 @@
       "idiom" : "ipad",
       "size" : "76x76",
       "scale" : "2x"
+    },
+    {
+      "idiom" : "ipad",
+      "size" : "83.5x83.5",
+      "scale" : "2x"
+    },
+    {
+      "idiom" : "ios-marketing",
+      "size" : "1024x1024",
+      "scale" : "1x"
     }
   ],
   "info" : {