[breaks api] Proxy no longer takes app as first parameter

We can use the app reference contained in RequestContext

example/main.dart

@@ -14,7 +14,6 @@ main() async {
   // Forward any /api requests to pub.
   // By default, if the host throws a 404, the request will fall through to the next handler.
   var pubProxy = new Proxy(
-    app,
     client,
     'https://pub.dartlang.org',
     publicPath: '/pub',
@@ -30,7 +29,6 @@ main() async {
 
   // Anything else should fall through to dartlang.org.
   var dartlangProxy = new Proxy(
-    app,
     client,
     'https://dartlang.org',
     timeout: timeout,

lib/src/proxy_layer.dart

@@ -11,7 +11,6 @@ final MediaType _fallbackMediaType = MediaType('application', 'octet-stream');
 class Proxy {
   String _prefix;
 
-  final Angel app;
   final http.Client httpClient;
 
   /// If `true` (default), then the plug-in will ignore failures to connect to the proxy, and allow other handlers to run.
@@ -25,7 +24,6 @@ class Proxy {
   final Duration timeout;
 
   Proxy(
-    this.app,
     this.httpClient,
     this.host, {
     this.port,
@@ -88,7 +86,7 @@ class Proxy {
 
         var body;
 
-        if (req.method != 'GET' && app.keepRawRequestBuffers == true) {
+        if (req.method != 'GET' && req.app.keepRawRequestBuffers == true) {
           body = (await req.parse()).originalBuffer;
         }
 

test/basic_test.dart

@@ -22,14 +22,12 @@ main() {
     testServer = await startTestServer();
 
     var proxy1 = new Proxy(
-      app,
       httpClient,
       testServer.address.address,
       port: testServer.port,
       publicPath: '/proxy',
     );
     var proxy2 = new Proxy(
-      app,
       httpClient,
       testServer.address.address,
       port: testServer.port,

test/pub_serve_test.dart

@@ -34,7 +34,6 @@ main() {
     var httpClient = new http.Client();
 
     layer = new Proxy(
-      app,
       httpClient,
       server.address.address,
       port: server.port,