Remove opcode from read, async_read (API Change):

fix #446

* Read signatures no longer include `opcode`

* stream::got_binary and stream::got_text inform the caller if
  the current incoming message is binary or text.

Actions Required:

* Remove the `opcode` reference parameter from calls to synchronous
  and asynchronous read functions, replace the logic with calls to
  stream::got_binary and stream::got_text instead.

test/websocket/ssl/ssl_server.cpp

@@ -130,14 +130,13 @@ public:
 
         // Receive Secure WebSocket message, print and close using Beast
         beast::multi_buffer b;
-        beast::websocket::opcode op;
-        ws.read(op, b);
+        ws.read(b);
         ws.close(beast::websocket::close_code::normal);
         try
         {
             for(;;)
             {
-                ws.read(op, b);
+                ws.read(b);
                 b.consume(b.size());
             }
         }