Publish all polls that are part of a downtime period.
Merge branch 'downtime_polls' into 'master'

Downtime polls
In the case of a failed poll store the entire error and result objects
in the poll record.  This ensures that we record as much information
as we have for diagnostic purposes.
Merge branch 'downtime_polls' into 'master'

Downtime polls
Added global tolerance of 1.
Merge branch 'tolerance' into 'master'

Tolerance
Added a User-Agent header.
Merge branch 'user-agent' into 'master'

User-Agent

Add a User-Agent header.  I also re-indented the callback, which makes the diff look somewhat more confusing than it is.