Update examples for api updates (#918)

Add deprecations for renamed purchase methods so Xcode can suggest the rename.
Update purchase methods for named completion block instead of _

Examples/LegacySwiftExample/SwiftExample/InitialViewController.swift

@@ -19,14 +19,14 @@ class InitialViewController: UIViewController {
     override func viewDidAppear(_ animated: Bool) {
         super.viewDidAppear(animated)
         
-        // Get the latest purchaserInfo to see if we have a pro cat user or not
-        Purchases.shared.purchaserInfo { (purchaserInfo, error) in
+        // Get the latest customerInfo to see if we have a pro cat user or not
+        Purchases.shared.getCustomerInfo { (customerInfo, error) in
             if let e = error {
                 print(e.localizedDescription)
             }
             
             // Route the view depending if we have a premium cat user or not
-            if purchaserInfo?.entitlements["pro_cat"]?.isActive == true {
+            if customerInfo?.entitlements["pro_cat"]?.isActive == true {
                 
                 // if we have a pro_cat subscriber, send them to the cat screen
                 let storyboard = UIStoryboard(name: "Main", bundle: nil)