This introduces a "purge_zones" toggle which, if enabled, ensures
zones not managed using the firewalld pillar get deleted.
Useful to enforce that only Salt managed zones exist and to clean
up pre-Salt data.

Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>

fixes #51

Document and test the accept rate limiting of the rich rule.

Signed-off-by: Arnaud Patard <apatard@hupstream.com>

Close #44.

Configuration description taken from:

* https://firewalld.org/documentation/man-pages/firewalld.conf.html

When specifying rich rules as a dictionary ipsets and services can be
specified as lists. They will be expanded out by the jinja template into
individual rich rules for the parent zone.

Now multiple sections ending with `services` can be defined for each in pillar
and all of them will get merged into one service block in the zone. The goal is
to keep backward compatibility while allowing different services to be defined
in different pillars. So basically have various parts of the pillar affecting
the firewall without need to define everything centrally. Helpful for the
exceptions to the rules.

```bash
firewalld-formula$ yamllint -s .
./pillar.example
  2:1       warning  missing document start "---"  (document-start)
  3:12      warning  truthy value should be one of [false, true]  (truthy)
  12:13     warning  truthy value should be one of [false, true]  (truthy)
  15:89     error    line too long (108 > 88 characters)  (line-length)
  19:13     warning  truthy value should be one of [false, true]  (truthy)
  30:89     error    line too long (363 > 88 characters)  (line-length)
  96:89     error    line too long (170 > 88 characters)  (line-length)
  108:15    error    wrong indentation: expected 12 but found 14  (indentation)
  115:13    error    empty value in block mapping  (empty-values)
  116:2     error    syntax error: found character '%' that cannot start any token
  152:89    error    line too long (112 > 88 characters)  (line-length)

./firewalld/defaults.yaml
  3:1       warning  missing document start "---"  (document-start)
```

update kitchen travis
fix ipsets.sls

See https://github.com/saltstack-formulas/firewalld-formula/pull/21#pullrequestreview-146958098

See https://github.com/saltstack-formulas/firewalld-formula/pull/21#pullrequestreview-146958098