Add ruby / rubygem

[zbal]

No ruby currently available, but we rely on compass / gem with grunt.

Need to find a way to:

• install ruby,
• install dependencies (ala php extension)

Dependencies are not configuration per-se so we may want to move it out of the way? Or we simply add them in the config as extensions ex.

configuration:
  - ruby:
    extensions:
      - gem
      - compass
      - etc.

[zbal]

Ruby package added, gems extension are installed globally.

configuration:
  ruby:
    gems:
      - compass