Rewrite the startup of bit

Author: shengyuan

src/board/Bit.js

@@ -54,14 +54,15 @@
 
   Bit.DEFAULT_SERVER = 'wss://ws.webduino.io:443';
 
-  proto.startup = async function () {
+  proto.startup = function () {
     this._isReady = true;
-    if (this._options.transport === 'serial') {
-      // wait for physical board ready to receive data from serialPort
-      await delay(0.5);
-      this.send([0xf0, 0x0e, 0x0c, 0xf7]);
-    }
     this.emit(BoardEvent.READY, this);
+    setTimeout(function() {
+      if (this._options.transport === 'serial') {
+        // wait for physical board ready to receive data from serialPort
+        this.send([0xf0, 0x0e, 0x0c, 0xf7]);
+      }  
+    }.bind(this), 500);
   };