Gitrob will now look for a file at `~/.gitrobsignatures` which it
expects to be a JSON document that follows the same structure as the
main signatures.json file. If the signatures are valid, it will be
loaded into the BlobObserver.
- The `--verify-ssl` command option did not properly set SSL configuration on
GitHub API clients.
- Setting GitHub access tokens with `--access-tokens` command option resulted
in an error.