Upgrade middleware to new style from aiohttp 2.3+

CHANGES.txt

@@ -4,7 +4,7 @@ CHANGES
 0.15.0 (2017-xx-xx)
 -------------------
 
--
+- Upgrade middleware to new style from aiohttp 2.3+
 
 -
 

aiohttp_jinja2/__init__.py

@@ -103,16 +103,15 @@ def wrapped(*args):
     return wrapper
 
 
+@web.middleware
 @asyncio.coroutine
-def context_processors_middleware(app, handler):
-    @asyncio.coroutine
-    def middleware(request):
-        request[REQUEST_CONTEXT_KEY] = {}
-        for processor in app[APP_CONTEXT_PROCESSORS_KEY]:
-            request[REQUEST_CONTEXT_KEY].update(
-                (yield from processor(request)))
-        return (yield from handler(request))
-    return middleware
+def context_processors_middleware(request, handler):
+
+    request[REQUEST_CONTEXT_KEY] = {}
+    for processor in request.app[APP_CONTEXT_PROCESSORS_KEY]:
+        request[REQUEST_CONTEXT_KEY].update(
+            (yield from processor(request)))
+    return (yield from handler(request))
 
 
 @asyncio.coroutine