fixes max_nesting for npm source installs

Fixes a syntax error in 3cc49c20 that results in the following converge error when `node['nodejs']['npm']['install_method'] == 'source'` :

```
ArgumentError
-------------
wrong number of arguments (2 for 1)
```
Merge pull request #33 from steve-jansen/npm-source-fix

fixes max_nesting for npm source installs