Add documentation for UINavigationBar extensions

Author: jwfriese

Documentation/UINavigationBar.md

@@ -0,0 +1,12 @@
+# UINavigationBar
+
+## Methods
+`public func tapTopItem(withTitle title: String)`
+
+Searches the `topItem` of a navigation bar for an item with a
+title equal to the parameter `title`. If found, it fires the action
+associated with that item.
+
+Raises a `FleetError` if a navigation bar item with the given title
+cannot be found, if there in the are no items in the navigation bar,
+or if the item's action is not properly set up.

README.md

@@ -25,6 +25,7 @@ Fleet extends UIKit classes in order to make it easier to test your code's inter
 - [UIBarButtonItem](./Documentation/UIBarButtonItem.md) - Provides convenience methods similar to those provided for UIButton.
 - [UIAlertController](./Documentation/UIAlertController.md) - Allows specs to simply tap on alert actions in order to test their behavior.
 - [UITabBarController](./Documentation/UITabBarController.md) - Provides convenience methods for selecting tabs.
+- [UINavigationBar](./Documentation/UINavigationBar.md) - Tap on items in a navigation bar.
 - [UITextField](./Documentation/UITextField.md) - Provides convenience methods for entering text. (iOS-only)
 - [UISwitch](./Documentation/UISwitch.md) - Provides convenience methods for interacting with switches in test. (iOS-only)
 - [UITextView](./Documentation/UITextView.md) - Provides convenience methods for entering text into a text view. (iOS-only)