Allow for a lower case 'yes' on teardown
- allow user to input 'yes' instead of 'YES' on teardown
- add .env to .gitignore
I just spent too much time trying to figure out why it wasn't tearing down my cluster with a bunch of false leads. I was typing 'yes' instead of 'YES'. I'm pretty sure I'll mess this up again the next time I try to use this project if it's long enough that I forget.