paas were trying to ascertain if notify was up by looking at '/', for cert
renewal. This commit adds the status endpoint to '/', so we're not mistakenly
left for our cert to expire
Also rename the 'elb' argument to 'simple' to be more descriptive.
The healthcheck is going to issue requests to `/_status?simple=true`
just to check that gunicorn is up and running - we don't need to go all
the way to the database, as this would have adverse impact when api is
under load.
The test this status check was doing does not reflect real traffic of Notify. It is typical for messages to be in 'sending' for a while (people turn off their phone for example).
- include travis build number
- renamed properties
- ELB version
- moved code all into health check
- changed health check to be on same URL for admin and api
