Don't use beanstalk client directly, subclass custodian/queue, or similar
to allow us to swap out the queue and stub it for testing.

The HTTP/HTTPS-probe should be pure Ruby.  Patrick will point me at symbiosis-monit

The alerter needs to be overhauled since it relies upon the old hash-based approach.

make Custodian::Parser::Macro a class.
Use that, and make sure that we return such a thing when we define a new one.