wrench@1.5.9: wrench.js is deprecated

I got this when installing today using `npm install -g node-lambda`.

```
npm WARN deprecated wrench@1.5.9: wrench.js is deprecated! 
You should check out fs-extra (https://github.com/jprichardson/node-fs-extra) 
for any operations you were using wrench for. Thanks for all the usage over the years.
```
