Added note for fixing PostgreSQL issue

[dokun1]

Hi Tim!!! 👋 Congratulations on your release!

I tried the sample, and I ran into an issue with PostgreSQL that ended up being easy to solve, but wasn't super obvious to fix. For those that may be confused by the issue, I've done the following:

1. I added a stopDB.sh script which will cut off the existing container you create with setupDB.sh.
2. I added to your README.md file with instructions on how to see if PostgreSQL is already running.
3. I added to your README.md file with one example of how to remove it.

I also went ahead and put all your bash scripts into a bin directory for the sake of organization. Thank you for making this!