* Add support for sending events to Sensu
Sensu is an alerting and monitoring service (and much more) that has a
nagios compatible check API.
This transport translates LibreNMS alerts into Sensu events, and sends
them to the agent API running on the same host as the poller.
The transport has a few options, but none of them are required - if the
Sensu agent is correctly configured, alerts will be sent as soon as the
transport is enabled.
There's a fair amount of code, as I've tried to translate as much data as
possible between LibreNMS and Sensu.
* Update Transports.md
* If alerted is 0, send an "ok" alert dated rrd.step / 2 seconds ago
This makes Sensu aware of the last time the check ran successfully (ish).
If we don't send the initial "ok", Sensu will either display 'unknown',
or an incorrectly high duration for the incident.
Alerted gets set to 1 after the first alert is sent.
We choose rrd.step / 2 as:
* rrd.step is the maximum time ago the check could have succeeded
* we halve it, so that if a check is flapping, it is not masked
Basically, we guess that the check fails around halfway through the time
since the poller last ran.
* Add additional metadata
* Improve codeclimate slightly
* Consider names that are 2 or 3 components long
