Adds note around a knonw version control issue

The NuGet client has a known bug that can cause the packages folder to still being added to version control -- even if it's excluded by a .tfignore/.gitignore file.
Adds a workaround for the source control issue

As Jeff pointed out, disabling the source control integration completely will workaround the issue.
Merge pull request #179 from terrajobst/patch-1

Adds note around a knonw version control issue