Fix reduce() error, rename environment variables

[tonygaetani]

There are two commits here. One for renaming the aws credential environment variables to something more common (at least in my experience) and another for when no instances are found so the script doesn't end with an uncaught exception.

[tonygaetani]

I'm willing to make a few more contributions if you'd like. For example region configuration and external configuration kind of stuff. I'm not sure if you're inactive for the moment or if you're just done with this project, but if you're not done with the project let me know and I'm happy to work on it!