optionally add email notifications

Added

• Added the option to subscribe to events by SNS email notification

improve input options

Added

• Add a variable to set the SNS topic name

Changed

• Change backup schedule variable to accept either cron or rate
• Update terraform and aws versions
• Move locals to the top of main.tf

Removed

• Remove outputs that are just a copy of input variables
• Remove unused aws iam key variables

pre-release

0.0.1

fix test