* Refactored install script (and .kitchen.yml) to support installing Chocolatey
in test-kitchen behind a proxy.
* Remove `node['chocolatey']['Uri']` attribute. Instead, install by downloading
the chocolatey.nupkg directly via Chef's `remote_file` resource. This lets users
install via Chef client.rb proxy settings instead of inheriting Internet Explorer
proxy settings.

* Add ChefSpec unit tests
* Add ServerSpec integration tests
* Gemfile: bump foodcritic to 5.0 and Berkshelf to 4.0

*	Changed helpers module namespacing
   	Renamed `ChocolateyHelpers` to `Chocolatey::Helpers`
   	Follow standard cookbook helper module namespacing of:
   	module <cookbook>
   	  module Helpers