Download and install powershell modules using ruby

[RyanJarv]

This will allow the powershell_module to work on Core installations of
Windows. It does however it adds a dependency on the rubyzip gem.

[chef-supermarket]

Hi. I am an automated pull request bot named Curry. There are commits in this pull request whose authors are not yet authorized to contribute to Chef Software, Inc. projects or are using a non-GitHub verified email address. To become authorized to contribute, you will need to sign the Contributor License Agreement (CLA) as an individual or on behalf of your company. You can read more on Chef's blog.

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• @RyanJarv

Please sign the CLA here.

[chef-supermarket]

Hi. Your friendly Curry bot here. Just letting you know that all commit authors have become authorized to contribute. I have added the "Signed CLA" label to this issue so it can easily be found in the future.

[smurawski]

Thanks for the PR. I've got a bit of manual testing to do, but I should be able to get this merged early next week.

[RyanJarv]

Thanks! Let me know if I can help in any way. FYI, Just fixed a typo in one of the doc lines I added.

[smurawski]

Merged in #63