fetch all input body in gaiohttp to work w/ non asyncio wsgi apps

I took the suggestion of @asvetlov. This change load first all the body
in RAM in the gaiohttp worker to handle classic WSGI application. This
is a temporary fix, it should be replaced asap by a streaming behaviour.
It does the trick anyway for most application since you're not supposed
to handle large body directly with gunicorn.

fix #803

examples/echo.py

@@ -0,0 +1,37 @@
+# -*- coding: utf-8 -
+#
+# This file is part of gunicorn released under the MIT license.
+# See the NOTICE for more information.
+#
+# Example code from Eventlet sources
+
+import os
+import pprint
+from wsgiref.validate import validator
+import sys
+
+from gunicorn import __version__
+#@validator
+def app(environ, start_response):
+    """Simplest possible application object"""
+
+    errors = environ['wsgi.errors']
+#    pprint.pprint(('ENVIRON', environ), stream=errors)
+
+    print(environ)
+    if environ['REQUEST_METHOD'].upper() != 'POST':
+        data = b'Hello, World!\n'
+    else:
+        data = environ['wsgi.input'].read()
+
+
+    status = '200 OK'
+
+    response_headers = [
+        ('Content-type','text/plain'),
+        ('Content-Length', str(len(data))),
+        ('X-Gunicorn-Version', __version__),
+        ("Test", "test тест"),
+    ]
+    start_response(status, response_headers)
+    return iter([data])

gunicorn/workers/gaiohttp.py

@@ -49,7 +49,8 @@ class AiohttpWorker(base.Worker):
 
     def factory(self, wsgi, host, port):
         proto = WSGIServerHttpProtocol(
-            wsgi, loop=self.loop,
+            wsgi, readpayload=True,
+            loop=self.loop,
             log=self.log,
             debug=self.cfg.debug,
             keep_alive=self.cfg.keepalive,