sensu server monitor

simple container that monitors sensu /info API and emails in case it fails twice in a row, designed to answer the age old questions of who watches the watchers?.

set the following envvars when running the container:

1. MAIL_FROM = the from mail address
2. MAIL_TO = the email address to send alerts to
3. SENSU_HOST = the sensu host fqdn\ip
4. SENSU_PORT = the sensu host port
5. CHECK_TIMEOUT = time to wait check attempts

after sending an alert email the container will wait 10 times the CHECK_TIMEOUT or 10 minutes (the bigger of the two) before checking again and re-alerting if needed.