Allow `gem build` from downloaded zip file

[bvandgrift]

This PR does the following:

• Uses Dir['**/*'] to collect files to include in the .gem file when git ls-files is unavailable (such as when one has downloaded the zip file due to environmental restrictions on git)
• Fixes a rubocop complaint
• Bumps a minor version number

[adamleff]

@bvandgrift thank you for opening this pull request.

Unfortunately, this change would be inconsistent with the gemspecs of our other plugins that we maintain, and our development workflow assumes a fully-working git environment where commands like git ls-files function correctly. For those reasons, we will not be able to accept your change.

Your change to lib/kitchen/driver/vra.rb to use #empty? rather than inspecting the size is a valid suggestion though, so I'll cherry-pick that on a separate PR and attribute that change to you.

Thanks in advance for your understanding. ~Adam