Added autocommit key word argument to create_pool

Autocommit default to false as key word argument to create pool method.

Author: magnamatt

docs/pool.rst

@@ -18,7 +18,7 @@ The basic usage is::
     def go()
         pool = yield from aiomysql.create_pool(host='127.0.0.1', port=3306,
                                                user='root', password='',
-                                               db='mysql', loop=loop)
+                                               db='mysql', loop=loop, autocommit=False)
 
         with (yield from pool) as conn:
             cur = yield from conn.cursor()