fix(plugins): have counter-cache use correct way of defining default values

lib/plugins/counter-cache.js

@@ -45,15 +45,12 @@ module.exports = (function() {
 
     newAttributes[this.columnName] = {
       type: DataTypes.INTEGER,
-      allowNull: false
-    };
-
-    // apparently you can't set defaultValues after model definition
-    this.source._defaultValues[this.columnName] = Utils._.partial(
+      allowNull: false,
+      defaultValue: Utils._.partial(
         Utils.toDefaultValue,
         0
-    );
-    this.source._hasDefaultValues = true;
+      )
+    };
 
     Utils.mergeDefaults(this.source.rawAttributes, newAttributes);