Increase max nesting on npm install check JSON parse

I was running into errors when using the npm_package LWRP:

```
JSON::NestingError: execute[install NPM package gulp] (/tmp/vagrant-chef-3/chef-solo-1/cookbooks/nodejs/providers/npm.rb line 6) had an error: JSON::NestingError: nesting of 20 is too deep
```

Increasing the max_nesting to 100 resolved this.