fix a bug that using `Instance::destroy()` under multiple primary keys

lib/instance.js

@@ -836,7 +836,10 @@ module.exports = (function() {
         return this.save(_.extend(_.clone(options), {hooks : false}));
         return this.save(_.extend(_.clone(options), {hooks : false}));
       } else {
       } else {
         where = {};
         where = {};
-        where[this.Model.rawAttributes[this.Model.primaryKeyAttribute].field] = this.get(this.Model.primaryKeyAttribute, {raw: true});
+        var primaryKeys = this.Model.primaryKeyAttributes;
+        for(var i = 0; i < primaryKeys.length; i++) {
+            where[this.Model.rawAttributes[primaryKeys[i]].field] = this.get(primaryKeys[i], { raw: true });
+        }
         return this.QueryInterface.delete(this, this.Model.getTableName(options), where, _.defaults(options, { type: QueryTypes.DELETE,limit: null}));
         return this.QueryInterface.delete(this, this.Model.getTableName(options), where, _.defaults(options, { type: QueryTypes.DELETE,limit: null}));
       }
       }
     }).tap(function() {
     }).tap(function() {