Update README.MD

Author: oxygen

README.MD

@@ -11,6 +11,7 @@ This library is tested in __browsers__ (>= IE10) and in __Node.js__ (>=7.8).
 Very simple usage allows for very easy application development: 
  * export methods in an endpoint (which extends JSONRPC.EndpointBase), and call those method remotely through a client (which extends JSONRPC.Client);
  * on bidirectional transports, there may be endpoints at both ends of a connection, or reversed roles (TCP client is a JSONRPC server, while TCP server is JSONRPC client).
+ * all remote invocations are asynchronous (multiple responses on the same connection are matched to the right waiting promises)
 
 ## Transports