ci: merge travis matrix, add `salt-lint` & `rubocop` to `lint` job

* Automated using https://github.com/myii/ssf-formula/pull/60

.rubocop.yml

+# -*- coding: utf-8 -*-
+# vim: ft=yaml
+---
+# General overrides used across formulas in the org
+Metrics/LineLength:
+  # Increase from default of `80`
+  # Based on https://github.com/PyCQA/flake8-bugbear#opinionated-warnings (`B950`)
+  Max: 88
+
+# Any offenses that should be fixed, e.g. collected via. `rubocop --auto-gen-config`

.salt-lint

+# -*- coding: utf-8 -*-
+# vim: ft=yaml
+---
+exclude_paths: []
+skip_list:
+  # Using `salt-lint` for linting other files as well, such as Jinja macros/templates
+  - 205  # Use ".sls" as a Salt State file extension
+  # Skipping `207` and `208` because `210` is sufficient, at least for the time-being
+  # I.e. Allows 3-digit unquoted codes to still be used, such as `644` and `755`
+  - 207  # File modes should always be encapsulated in quotation marks
+  - 208  # File modes should always contain a leading zero
+tags: []
+verbosity: 1

.travis.yml

 # -*- coding: utf-8 -*-
 # vim: ft=yaml
 ---
+## Machine config
 dist: bionic
+
+## Stages and jobs matrix
 stages:
-  - lint
+  - test
   - name: release
     if: branch = master AND type != pull_request
-
 jobs:
+  allow_failures:
+    - env: Lint_rubocop
+  fast_finish: true
   include:
-    # Define the `lint` stage (runs `yamllint` and `commitlint`)
-    - stage: lint
-      language: node_js
+    ## Define the test stage that runs the linters (and testing matrix, if applicable)
+
+    # Run all of the linters in a single job (except `rubocop`)
+    - language: node_js
       node_js: lts/*
+      env: Lint
+      name: 'Lint: salt-lint, yamllint & commitlint'
       before_install: skip
       script:
+        # Install and run `salt-lint`
+        - pip install --user salt-lint
+        - git ls-files | grep '\.sls$\|\.jinja$\|\.j2$\|\.tmpl$'
+                       | xargs -I {} salt-lint {}
         # Install and run `yamllint`
         # Need at least `v1.17.0` for the `yaml-files` setting
         - pip install --user yamllint>=1.17.0
         - npm install @commitlint/config-conventional -D
         - npm install @commitlint/travis-cli -D
         - commitlint-travis
-    # Define the release stage that runs `semantic-release`
+    # Run the `rubocop` linter in a separate job that is allowed to fail
+    # Once these lint errors are fixed, this can be merged into a single job
+    - language: node_js
+      node_js: lts/*
+      env: Lint_rubocop
+      name: 'Lint: rubocop'
+      before_install: skip
+      script:
+        # Install and run `rubocop`
+        - gem install rubocop
+        - rubocop -d
+
+    ## Define the release stage that runs `semantic-release`
     - stage: release
       language: node_js
       node_js: lts/*
+      env: Release
+      name: 'Run semantic-release inc. file updates to AUTHORS, CHANGELOG & FORMULA'
       before_install: skip
       script:
         # Update `AUTHORS.md`

.yamllint

   # Default settings
   - '*.yaml'
   - '*.yml'
+  - .salt-lint
   - .yamllint
   # SaltStack Formulas additional settings
   - '*.example'

Gemfile

-source "https://rubygems.org"
+# frozen_string_literal: true
+
+source 'https://rubygems.org'
 
 gem 'kitchen-docker', '>= 2.9'
-gem 'kitchen-salt', '>= 0.6.0'
 gem 'kitchen-inspec', '>= 1.1'
-
+gem 'kitchen-salt', '>= 0.6.0'

bin/kitchen

 # this file is here to facilitate running it.
 #
 
-require "pathname"
-ENV["BUNDLE_GEMFILE"] ||= File.expand_path("../../Gemfile",
-  Pathname.new(__FILE__).realpath)
+require 'pathname'
+ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile',
+                                           Pathname.new(__FILE__).realpath)
 
-bundle_binstub = File.expand_path("../bundle", __FILE__)
+bundle_binstub = File.expand_path('bundle', __dir__)
 
 if File.file?(bundle_binstub)
   if File.read(bundle_binstub, 300) =~ /This file was generated by Bundler/
     load(bundle_binstub)
   else
-    abort("Your `bin/bundle` was not generated by Bundler, so this binstub cannot run.
-Replace `bin/bundle` by running `bundle binstubs bundler --force`, then run this command again.")
+    abort(
+      'Your `bin/bundle` was not generated by Bundler, '\
+      'so this binstub cannot run.  Replace `bin/bundle` by running '\
+      '`bundle binstubs bundler --force`, then run this command again.'
+    )
   end
 end
 
-require "rubygems"
-require "bundler/setup"
+require 'rubygems'
+require 'bundler/setup'
 
-load Gem.bin_path("test-kitchen", "kitchen")
+load Gem.bin_path('test-kitchen', 'kitchen')