provide file_version and product_version for windows files

[chris-rock]

fixes inspec/inspec#858

[stevendanna]

👍 seems reasonable.

[chris-rock]

I had to remove the test for appveyor:

  it 'check file versioning on windows' do
    # may break when appveyor upgrades
    file = conn.file("C:/Ruby21/bin/ruby.exe")
    file.product_version.must_equal '...'
    file.file_version.must_equal '...'
  end