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)
```

salt/defaults.yaml

@@ -1,20 +1,21 @@
 # -*- coding: utf-8 -*-
 # vim: ft=yaml
+---
 salt:
   version: ''
   rootuser: root
   rootgroup: root
-  install_packages: True
-  use_pip: False
-  clean_config_d_dir: True
-  restart_via_at: False
+  install_packages: true
+  use_pip: false
+  clean_config_d_dir: true
+  restart_via_at: false
 
   config_path: /etc/salt
 
-  minion_remove_config: False
-  master_remove_config: False
-  minion_config_use_TOFS: False
-  master_config_use_TOFS: False
+  minion_remove_config: false
+  master_remove_config: false
+  minion_config_use_TOFS: false
+  master_config_use_TOFS: false
 
   minion_service: salt-minion
   master_service: salt-master
@@ -36,22 +37,22 @@ salt:
 
   gitfs:
     dulwich:
-      install_from_source: True
+      install_from_source: true
     pygit2:
-      install_from_source: True
+      install_from_source: true
       version: 0.23.0
       git:
         # if not false, should be state name
-        require_state: False
+        require_state: false
         install_from_package: git
       libgit2:
         version: 0.23.0
-        install_from_source: True
+        install_from_source: true
         build_parent_dir: /usr/src/
         # hash necessary until github issue #9272 is addressed
         download_hash: 683d1164e361e2a0a8d52652840e2340
     gitpython:
-      install_from_source: False
+      install_from_source: false
 
   cloud:
     template_sources:
@@ -60,12 +61,12 @@ salt:
       maps: salt://salt/files/cloud.maps.d
 
 salt_formulas:
-  checkout_orig_branch: False
+  checkout_orig_branch: false
   git_opts:
     default:
       baseurl: https://github.com/saltstack-formulas
       basedir: /srv/formulas
-      update: False
+      update: false
       options:
         rev: master
         output_loglevel: 'quiet'