Ability to unit test variables also

[Thiago Nache Carvalho]

Currently we can only test values but we may want to test some variables.

{
  "variables": {

  }
}

The transform function should also store the values inside of this block into the type Resource which will need an extra field probably called Variables which is going to be a map[string]string.

The functions Contains and Equal should be modified to consider the new data.

Please, also add respective tests for the new function 😄