Swift support for NetworkPlugin (#201)

Summary:
Solves #173

- [x] Add plugins in the sonarkit xcodeproj so that its easy to debug
- [x] Get rid off the c++ in the headers
- [x] Add example to hit network requests and validate

Have a look at the screen shot below ✨⭐️⚡️

<img width="1677" alt="screen shot 2018-08-02 at 12 46 07 pm" src="https://user-images.githubusercontent.com/3865908/43581809-22efe4fe-9652-11e8-9424-f279d07c5c81.png">
Pull Request resolved: https://github.com/facebook/flipper/pull/201

Reviewed By: danielbuechele

Differential Revision: D9132157

Pulled By: priteshrnandgaonkar

fbshipit-source-id: 2b425506961f02eb2bf629c2bcab0da6e7ce5bb0

iOS/SampleSwift/SampleSwift/AppDelegate.swift

@@ -17,7 +17,8 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
 //    let layoutDescriptorMapper = SKDescriptorMapper(defaults: ())
 //    SonarKitLayoutComponentKitSupport.setUp(descriptorMapper: layoutDescriptorMapper)
 //    client.addPlugin(SonarKitLayoutPlugin(rootNode: application, descriptorMapper: layoutDescriptorMapper))
-//    client.addPlugin(SonarKitNetworkPlugin(networkAdapter: SKIOSNetworkAdapter()))
+
+    client?.add(SonarKitNetworkPlugin(networkAdapter: SKIOSNetworkAdapter()))
     client?.start()
 
     let storyboard = UIStoryboard(name: "MainStoryBoard", bundle: nil)