1.9.0

Changes since 1.8:

REQUIRE PYTHON >= 3.5
Switch to distribution as a pip package! You can now "pip install simplemonitor"
Add memory monitor
Add Ring doorbell monitor (checks battery level)
Add support for checking file is not too large
Add support for running a command when a monitor recovers
Add support for reloading config on the fly
Fixes to compound monitor logic
HTTP monitor can check both return code and regexp now
Update pkgaudit monitor to chase new output format
DNS monitor can check response is NXDOMAIN
Many code quality improvements (I hope)