v1.1: Improved (i.e. less annoying) alerts!

We've improved something!

This version adds a check of the previously sent alert on Slack (if it exists, of course), which prevents double-posting of alerts. Previously, if an alert was active and the application was restarted, the alert would post again.

We accomplish this by hashing the alert and including it in the Slack post in context. This has the added benefit of making it easy to recognize if an alert changed, rather than reading through a whole bunch of alert text to see if an updated was added, etc.

Initial release

This release pulls RPIAlert out of slack-integrations and moves it into its own repo. Now, it's able to run in its own Docker container and be auto-deployed without the hassle of any other code.