* Automated using https://github.com/myii/ssf-formula/pull/50

* Semi-automated using https://github.com/myii/ssf-formula/pull/18
* Close #174

* Semi-automated using `ssf-formula` (v0.5.0)
* Fix errors shown below:

```bash
php-formula$ $(grep "\- yamllint" .travis.yml | sed -e "s:^\s\+-\s\(.*\):\1:")
./test/integration/default/inspec.yml
  1:1       warning  missing document start "---"  (document-start)

pillar.example
  3:1       warning  missing document start "---"  (document-start)
  7:22      warning  truthy value should be one of [false, true]  (truthy)
  8:22      warning  truthy value should be one of [false, true]  (truthy)
  10:22     warning  truthy value should be one of [false, true]  (truthy)
  16:17     warning  truthy value should be one of [false, true]  (truthy)
  41:12     error    wrong indentation: expected 10 but found 11  (indentation)
  46:27     warning  truthy value should be one of [false, true]  (truthy)
  70:18     warning  truthy value should be one of [false, true]  (truthy)
  74:19     warning  truthy value should be one of [false, true]  (truthy)
  83:22     warning  truthy value should be one of [false, true]  (truthy)
  97:22     warning  truthy value should be one of [false, true]  (truthy)
  107:89    error    line too long (93 > 88 characters)  (line-length)
  118:20    warning  truthy value should be one of [false, true]  (truthy)
  126:14    error    wrong indentation: expected 12 but found 13  (indentation)
  126:23    warning  truthy value should be one of [false, true]  (truthy)
  151:20    warning  truthy value should be one of [false, true]  (truthy)
  177:19    warning  truthy value should be one of [false, true]  (truthy)
  197:25    warning  truthy value should be one of [false, true]  (truthy)
```

* Automated using `ssf-formula` (v0.1.0-rc.1)

* Completes #179
* Fix testing on `develop` images and enable in the matrix