0.3.3: Lifeguard 0.4.2; Add `respawn_limit` attribute

* Update default to Lifeguard 0.4.2
* Add `respawn_limit` boolean attribute to service resource. Determines
  whether "respawn limit" line should be added to upstart config.
  Defaults to true.
* Add test for `respawn_limit`
* Update Berksfile to Berkshelf 3.0 format
* Remove old Gemfile... Use ChefDK instead