npm package.json author can be a string

Hey, after the #458 fix, I was still running into a bug. 

The package.json author can be a string encoded as "My Name <my.email@here.com>". The code was assuming a hash and calling "fetch" on a String.

This is a minimal fix and leaves open the problem of better validation of a string author for future implementation. Only an empty string check is implemented.

Also, latest RVM uses .ruby-version and .ruby-gemset, I added those to .gitignore