Added a global logger and added a valid token check.

apps/nginx/nginx.conf

packages/python/src/snip/__main__.py

packages/python/src/snip/logger.py

packages/python/src/snip/token/__main__.py

packages/python/src/snip/token/storage/file_store.py

packages/python/src/snip/token/storage/keyring_store.py

packages/python/src/snip/token/token.py