Upgrade role and fix dependencies

[dortegau]

Prerequisites

• Put an X between the brackets on this line if you have done all of the following:
  • Checked that your issue isn't already filled: https://github.com/issues?utf8=✓&q=is%3Aissue+user%3Aidealista
  • Checked that there is not already provided the described functionality

Description

It would be nice if this role:

• Use Ansible >= 2.4.5.0 and Molecule >= 2.0
• Use Pipenv to make a reproducible testing environment under Travis (and to be used for other developers without spending time solving some weird dependency problems 😄)
• Use Goss instead of Testinfra