Untested backup.rb changes.

I don't have the ability to test these changes, so i'll leave it up to
@mutewinter to test them and modify them if needed, but they should work
in theory.

Also updated the ReadMe to add new .env variables
More options + Moved the shared block to the right place, oops

Had the shared config options in the wrong place, also added more
options
So long Showbot!

More genericizing, pushed the last group of Showbot references to the
config