Preferred, Not Preferred Ordering Maintained

When example are given throughout the guide, it shows the preferred instance before the not preferred instance. However, in [unused code](https://github.com/raywenderlich/swift-style-guide#unused-code) this pattern is reversed, which may lead to confusion. For the sake of clarity and consistency, the Preferred section is now placed above the Not Preferred section, as is done throughout the rest of the style guide.

Author: BrandonB1

README.markdown

@@ -219,6 +219,13 @@ Unused (dead) code, including Xcode template code and placeholder comments shoul
 
 Aspirational methods not directly associated with the tutorial whose implementation simply calls the superclass should also be removed. This includes any empty/unused UIApplicationDelegate methods.
 
+**Preferred:**
+```swift
+override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
+  return Database.contacts.count
+}
+```
+
 **Not Preferred:**
 ```swift
 override func didReceiveMemoryWarning() {
@@ -236,13 +243,6 @@ override func tableView(_ tableView: UITableView, numberOfRowsInSection section:
   return Database.contacts.count
 }
 
-```
-
-**Preferred:**
-```swift
-override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
-  return Database.contacts.count
-}
 ```
 ### Minimal Imports