RC1: Pipenv + new checks: reminder, ssh-command

We are happy to announce that we prepare for a new stable release. This is a release candidate of 1.7

Features:

• Pipenv support to have repeatable environments, with dependencies exactly always the same on each installation
• Bump of dependencies versions
• Improvements to the CI pipelines
• ssh-command check that executes remote command and expects exit code and output contains phrases
• reminder check that alerts when the date is coming, supports recurring events