Retrieve four things from the web with concurrency

Add a simple example to show how to create a client that gathers multiple web resources _concurrently_ .

I am not sure if this example is serial or concurrent.  :-(  If it is serial then it would be quite helpful for readers to understand how to make it concurrent.

README.rst

@@ -51,6 +51,31 @@ To retrieve something from the web:
           print(html)
 
 
+To retrieve four things from the web with concurrency:
+
+.. code-block:: python
+
+  import aiohttp
+  import asyncio
+
+  async def fetch(session, url):
+      with aiohttp.Timeout(10):
+          async with session.get(url) as response:
+              return await response.text()
+
+  URLS = '''http://python.org
+            http://golang.org
+            http://perl.org
+            http://ruby-lang.org'''.split()
+
+  if __name__ == '__main__':
+      loop = asyncio.get_event_loop()
+      with aiohttp.ClientSession(loop=loop) as session:
+          coroutines = [fetch(session, url) for url in URLS]
+          pages = [loop.run_until_complete(coroutine) for coroutine in coroutines]
+          for url, page in zip(URLS, pages):
+              print('{:>15}\n{}\n{:.100}\n'.format(url, '=' * len(url), page))
+
 Server
 ^^^^^^