Mention 14.04 & 12.10 sunset
13.10 is EOL in ~2 months & there's a successor
Zero down-time deploy and server checks

This change makes Dokku start up the new container, run a set of checks
against it, and only switch traffic over to the new containers if all
checks complete successfully. No requests are dropped during the switch
over.

To specify checks, add a CHECKS file to the root of your project
directory. This is a text file with one line per check. Empty lines and
lines starting with # are ignored.

A check is a relative URL and may be followed by expected content from
the page, for example:

  /about     Our Amazing Team

Even if you don’t use any checks, this change will prevent downtime
during switching from old to new container.

See: https://labnotes.org/zero-downtime-deploy-with-dokku/
Merge remote-tracking branch 'downtime/zero-downtime' into zerodowntime

* downtime/zero-downtime:
  Zero down-time deploy and server checks
  13.10 is EOL in ~2 months & there's a successor
  Mention 14.04 & 12.10 sunset
Fixes progrium/dokku#482 - Can't use config:set to set parameters values with spaces

(cherry picked from commit 52a2db0fbdda263a65fc6ffe54d523798d3bb749)

Conflicts:
	plugins/config/commands