[FEATURE] - Clarify Git Repo Requirement

[ghost]

Pull request checklist

Before submitting your PR, please review the following checklist:

• Consider adding a unit test if your PR resolves an issue.
• All new and existing tests pass locally (palm test)
  ** error: /bin/bash: black: command not found ==> python3 -m pytest instead
• Lint (palm lint) has passed locally and any fixes were made for failures
  ** error: /bin/bash: black: command not found ==> black --skip-string-normalization --exclude="\.tpl\.py" .
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

Breaking changes

• Check if this pull request introduces a breaking change

What does this implement/fix? Explain your changes.

• Running palm in a directory that is not a Git repo raises a confusing error message. This update guides the user and updates the documentation
• Rearranged the config and get_current_branch to make it error before the config check
• Black formatted a few files

[jakeberesford-palmetto]

Murphy, first off - thanks for contributing to Palm with this PR!

Palm was developed initially to work within the context of a project, which should be a live git repository. Ethan and I have been talking about broadening that scope to facilitate onboarding and set up in issue #12

I have a branch started (spike/setup-machine) where I resolved this error and added some new functionality around the bigger idea of enabling new user onboarding. I'm going to close this PR out as I expect we will pursue a larger feature here. If you'd like to be involved in that implementation, feel free to branch from my spike and work with me on that approach!