Update index.js

With the parameter 'true',it doesn't work.Maybe cause by js.merge.


with 'true',error info
```
RangeError: Maximum call stack size exceeded
      at String.match (native)
      at typeOf (D:\xuebi\node_modules\koa-hbs\node_modules\merge\merge.js:67:36)
      at clone (D:\xuebi\node_modules\koa-hbs\node_modules\merge\merge.js:39:11)
      at clone (D:\xuebi\node_modules\koa-hbs\node_modules\merge\merge.js:57:21)
      at clone (D:\xuebi\node_modules\koa-hbs\node_modules\merge\merge.js:57:21)
      at clone (D:\xuebi\node_modules\koa-hbs\node_modules\merge\merge.js:49:21)
      at clone (D:\xuebi\node_modules\koa-hbs\node_modules\merge\merge.js:57:21)
      at clone (D:\xuebi\node_modules\koa-hbs\node_modules\merge\merge.js:57:21)
      at clone (D:\xuebi\node_modules\koa-hbs\node_modules\merge\merge.js:49:21)
      at clone (D:\xuebi\node_modules\koa-hbs\node_modules\merge\merge.js:57:21)
```