feat: use semantic-release cross-formula standard structure

* Semi-automated using https://github.com/myii/ssf-formula/pull/31
* Includes:
  - Update TOFS
  - Use `bin/kitchen`
  - Use `dist: bionic` in Travis
  - Add `yamllint` and apply rules
  - Use `pillars_from_files` throughout
  - Replace EOL images in Kitchen & Travis
  - Add `develop` images in Kitchen & Travis
* Fix (or ignore)  errors shown below:

```bash
salt-formula$ yamllint -s .
./pillar.example
  1:1       warning  missing document start "---"  (document-start)
  5:23      warning  truthy value should be one of [false, true]  (truthy)
  8:25      warning  truthy value should be one of [false, true]  (truthy)
  11:25     warning  truthy value should be one of [false, true]  (truthy)
  19:21     warning  truthy value should be one of [false, true]  (truthy)
  40:89     error    line too long (108 > 88 characters)  (line-length)
  41:89     error    line too long (112 > 88 characters)  (line-length)
  43:89     error    line too long (112 > 88 characters)  (line-length)
  45:89     error    line too long (110 > 88 characters)  (line-length)
  47:89     error    line too long (89 > 88 characters)  (line-length)
  74:27     warning  truthy value should be one of [false, true]  (truthy)
  82:9      error    wrong indentation: expected 10 but found 8  (indentation)
  101:14    warning  truthy value should be one of [false, true]  (truthy)
  102:20    warning  truthy value should be one of [false, true]  (truthy)
  103:89    error    line too long (119 > 88 characters)  (line-length)
  121:7     warning  comment not indented like content  (comments-indentation)
  122:24    error    syntax error: found character '%' that cannot start any token
  310:89    error    line too long (102 > 88 characters)  (line-length)
  330:89    error    line too long (113 > 88 characters)  (line-length)
  433:1     error    too many blank lines (1 > 0)  (empty-lines)

./salt/osmap.yaml
  4:2       error    syntax error: found character '%' that cannot start any token
  6:89      error    line too long (93 > 88 characters)  (line-length)
  22:89     error    line too long (137 > 88 characters)  (line-length)
  23:89     error    line too long (134 > 88 characters)  (line-length)
  33:89     error    line too long (149 > 88 characters)  (line-length)
  34:89     error    line too long (146 > 88 characters)  (line-length)

./salt/osfamilymap.yaml
  4:2       error    syntax error: found character '%' that cannot start any token
  6:89      error    line too long (94 > 88 characters)  (line-length)
  24:89     error    line too long (149 > 88 characters)  (line-length)
  25:89     error    line too long (146 > 88 characters)  (line-length)
  39:89     error    line too long (105 > 88 characters)  (line-length)
  40:89     error    line too long (127 > 88 characters)  (line-length)
  56:89     error    line too long (101 > 88 characters)  (line-length)

./salt/ospyvermap.yaml
  4:1       warning  missing document start "---"  (document-start)

./salt/defaults.yaml
  3:1       warning  missing document start "---"  (document-start)
  7:21      warning  truthy value should be one of [false, true]  (truthy)
  8:12      warning  truthy value should be one of [false, true]  (truthy)
  9:23      warning  truthy value should be one of [false, true]  (truthy)
  10:19     warning  truthy value should be one of [false, true]  (truthy)
  14:25     warning  truthy value should be one of [false, true]  (truthy)
  15:25     warning  truthy value should be one of [false, true]  (truthy)
  16:27     warning  truthy value should be one of [false, true]  (truthy)
  17:27     warning  truthy value should be one of [false, true]  (truthy)
  39:28     warning  truthy value should be one of [false, true]  (truthy)
  41:28     warning  truthy value should be one of [false, true]  (truthy)
  45:24     warning  truthy value should be one of [false, true]  (truthy)
  49:30     warning  truthy value should be one of [false, true]  (truthy)
  54:28     warning  truthy value should be one of [false, true]  (truthy)
  63:25     warning  truthy value should be one of [false, true]  (truthy)
  68:15     warning  truthy value should be one of [false, true]  (truthy)
```

test/integration/2018-3/pkgs_spec.rb

@@ -1,12 +1,10 @@
 case os[:name]
 when 'centos'
-  version = '2018.3.4-1.el6'
+  version = '2018.3.4-1.el7'
 when 'debian', 'ubuntu'
   version = '2018.3.4+ds-1'
-when 'opensuse'
-  version = '2018.3.0-42.1'
 when 'fedora'
-  version = '2018.3.0-1.fc28'
+  version = '2018.3.2-5.fc29'
 end
 
 control 'salt packages' do

test/integration/2019-2/pkgs_spec.rb

@@ -2,7 +2,9 @@ case os[:name]
 when 'centos'
   version = '2019.2.0-1.el7'
 when 'fedora'
-  version = '2019.2.0-1.fc29'
+  version = '2019.2.0-1.fc30'
+when 'opensuse'
+  version = '2019.2.0-lp150.3.33.1'
 when 'debian', 'ubuntu'
   version = '2019.2.0+ds-1'
 end

test/integration/develop/pkgs_spec.rb

@@ -0,0 +1,12 @@
+control 'salt packages' do
+  title 'should be installed'
+
+  %w(
+    salt-master
+    salt-minion
+  ).each do |p|
+    describe package(p) do
+      it { should be_installed }
+    end
+  end
+end

test/integration/develop/service_spec.rb

@@ -0,0 +1,13 @@
+control 'salt services' do
+  title 'should be running'
+
+  %w(
+    salt-master
+    salt-minion
+  ).each do |p|
+    describe service(p) do
+      it { should be_enabled }
+      it { should be_running }
+    end
+  end
+end

test/salt/pillar/develop-py3.sls

@@ -0,0 +1,6 @@
+# -*- coding: utf-8 -*-
+# vim: ft=yaml
+---
+salt:
+  release: 'latest'
+  py_ver: 'py3'

test/salt/pillar/salt.sls

@@ -0,0 +1,23 @@
+# -*- coding: utf-8 -*-
+# vim: ft=yaml
+---
+salt:
+  master:
+    fileserver_backend:
+      - rootfs
+    file_roots:
+      base:
+        - /srv/salt
+    pillar_roots:
+      base:
+        - /srv/pillar
+  minion:
+    master: localhost
+    fileserver_backend:
+      - rootfs
+    file_roots:
+      base:
+        - /srv/salt
+    pillar_roots:
+      base:
+        - /srv/pillar

test/salt/pillar/v2017-7-py2.sls

@@ -0,0 +1,6 @@
+# -*- coding: utf-8 -*-
+# vim: ft=yaml
+---
+salt:
+  release: '2017.7'
+  py_ver: 'py2'

test/salt/pillar/v2018-3-py2-forced-version.sls

@@ -0,0 +1,7 @@
+# -*- coding: utf-8 -*-
+# vim: ft=yaml
+---
+salt:
+  release: '2018.3'
+  py_ver: 'py2'
+  version: '2018.3.2-5.fc29'

test/salt/pillar/v2018-3-py2.sls

@@ -0,0 +1,6 @@
+# -*- coding: utf-8 -*-
+# vim: ft=yaml
+---
+salt:
+  release: '2018.3'
+  py_ver: 'py2'

test/salt/pillar/v2019-2-py2.sls

@@ -0,0 +1,6 @@
+# -*- coding: utf-8 -*-
+# vim: ft=yaml
+---
+salt:
+  release: '2019.2'
+  py_ver: 'py2'

test/salt/pillar/v2019-2-py3.sls

@@ -0,0 +1,6 @@
+# -*- coding: utf-8 -*-
+# vim: ft=yaml
+---
+salt:
+  release: '2019.2'
+  py_ver: 'py3'