release v0.3.0 (2015-09-04)

• Update chef links to use chef.io domain.
• Update contact information and links after migration.
• Update RuboCop to version 0.33.0.
• metadata: Add source_url and issues_url links.
• Documentation:
  • README: Improve description.
• Testing:
  • Update Gemfile dependencies and Kitchen platforms.
  • Move ChefSpec tests to test/unit.
  • Use ChefSpec::SoloRunner to make unit tests faster.
  • Integrate tests with should_not gem.