Log Message:
Update ruby-mixlib-cli to 1.7.0.

1.7.0							2016/07/06

* Support two-argument procs for reducer style

1.6.0							2016/05/05

* Properly pass options during inheritance
* Added option key ':in' to specify that option value should be included in
  the given list
* Fixed ruby-warning "instance variable @{ivar} not initialized". - Kenichi
  Kamiya
* Documented CLI arguments. - C Chamblin
* Added rake, rdoc, and rspec and development dependencies
* Removed the contributions.md document and merged it with the changelog
* Updated code to comply with chefstyle style guidelines
* Fixed a missing comma from an example in the readme
* Ship the Gemfile so that tests can run from the Gem