Suggestion: Dorothy install process should detect if a user repo was renamed

[balupton]

From #235 (comment)

@oscarvarto specified oscarvarto/dotfiles during installation, which did not exist, but because it did exist at some point and was renamed to oscarvarto/dotfiles-old or something of the like, git cloned the renamed directory.

We should test if a rename has occurred and ask the user if they are sure.

There is significant refactoring of the install process in the dev-strongbox branch so once those are merged, then this should be considered.