Switch assetDetail from wapi to sapi

As per #363 WAPI endpoints will disappear on Aug 1.
Calling this function using sapi will now return the same structure as for wapi to provide backwards compatibility

Author: ePascalC

php-binance-api.php

@@ -647,8 +647,21 @@ public function exchangeInfo()
 
     public function assetDetail()
     {
-        $params["wapi"] = true;
-        return $this->httpRequest("v3/assetDetail.html", 'GET', $params, true);
+        $params["sapi"] = true;
+        $arr = $this->httpRequest("v1/asset/assetDetail", 'GET', $params, true);
+        // wrap into another array for backwards compatibility with the old wapi one
+        if (!empty($arr['BTC']['withdrawFee'])) {
+            return array(
+                'success'     => 1,
+                'assetDetail' => $arr,
+                );
+        } else {
+            return array(
+                'success'     => 0,
+                'assetDetail' => array(),
+                );
+            
+        }
     }
 
     public function userAssetDribbletLog()