Bug fixes in converter.rb and new quickstart guide

I am new to Ruby and had trouble running this script. I had to move the AUTHORS_FILE definition outside the method definition to resolve an error about assigning variables to a constant. I also quoted the parameters the best I could figure out to resolve a problem changing the working directory in vault due to a problem with spaces in the vault project path causing the command to silently fail and allowing the program to continue with an incorrect mapping.

Because I'm new to Ruby, I didn't have an environment to run this in so I included a quickstart for anything that is in my shoes. Ruby 1.9 complained at the require 'converter' line but this could probably be a quick change to require_relative. It hadn't fixed the problem for me at the time due to the authors problem and I already reverted to 1.8. That's when I hit the problem with nokogiri wanting Ruby 1.9+ and learned how to specify an older version.

Long story short - these couple changes were all I needed and the script runs like a champ. Great work!