fix documentation typos (#374)

Author: Molkree

docs/client.rst

@@ -131,7 +131,7 @@ When a server emits an event to a client, it can optionally provide a
 callback function, to be invoked as a way of acknowledgment that the server
 has processed the event. While this is entirely managed by the server, the
 client can provide a list of return values that are to be passed on to the
-callback function set up by the server. This is achieves simply by returning
+callback function set up by the server. This is achieved simply by returning
 the desired values from the handler function::
 
     @sio.event
@@ -197,7 +197,7 @@ that belong to a namespace can be created as methods of a subclass of
 
     sio.register_namespace(MyCustomNamespace('/chat'))
 
-For asyncio based severs, namespaces must inherit from
+For asyncio based servers, namespaces must inherit from
 :class:`socketio.AsyncClientNamespace`, and can define event handlers as
 coroutines if desired::