copy dotfiles also for terraspace build, this allow tfenv to use .terraform-version

[tongueroo]

This is a 🐞 bug fix.
This is a 🙋‍♂️ feature or enhancement.

• I've added tests (if it's a bug, feature or enhancement)
• I've adjusted the documentation (if it's a feature or enhancement)
• The test suite passes (run bundle exec rspec to verify this)

Summary

Context

Fixes #127

How to Test

echo 1.0.3 > app/stacks/demo/.terraspace-version
terraspace build demo
cat .terraspace-cache/us-west-2/dev/stacks/demo/.terraform-version 

Version Changes

Patch