support of windows guests
make `rake rubocop` a bit more happy
Refactor `#windows_guest?` helper

The helper can now be used anywhere.
Simplify install script calculation logic

We can take advantage of the very helpful 301 redirect of:

https://www.getchef.com/chef/install.msi
Update `install.bat` script to accept version parameter
Rubocop: fix outstanding errors and ignore method/class length
Rubocop: expand linting to Rakefile and Vagrantfiles
Rubocop: fix outstanding linting errors
Merge pull request #60 from schisamo/windows-support

Windows Support Part Deux