Follow Ansible Galaxy best practices

[ferrarimarco]

Currently this cookiecutter is not following at least three of the Ansible Galaxy best practices:

1. README.md should be formatted with markdown: see pull request Use Markdown in README. For #8 #9
2. Prefix variable names with the role name: can be fixed by editing this line
3. Integrate your roles with Travis CI: for this one I opened an issue (Implement a test infrastructure #6) and a pull request (Implement a test infrastructure. For #6 #7)

Thoughts?

[ferrarimarco]

@iknite I implemented point no.2 here in my fork. Let me know if you are interested, I can prepare a PR.