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.

examples/websocket_sync_echo_server.hpp

@@ -207,15 +207,14 @@ private:
         }
         for(;;)
         {
-            beast::websocket::opcode op;
             beast::multi_buffer b;
-            ws.read(op, b, ec);
+            ws.read(b, ec);
             if(ec)
             {
                 auto const s = ec.message();
                 break;
             }
-            ws.binary(op == beast::websocket::opcode::binary);
+            ws.binary(ws.got_binary());
             ws.write(b.data(), ec);
             if(ec)
                 break;