Gmail-api-wrapper

Enhancements:

- [x] Read client ID & secret from `~/.credentials/client_secret.json`
- [x] Remove `GAW_CLIENT_SECRET_FILE_PATH` env variable
- [x] Arrange import statements in the correct order

Features:

- [x] Allow composing and sending a new message without an attachment
- [x] Allow creating a new label
- [x] Wrap write API helper methods inside `GmailAPIWriteHelper` class
- [x] Add `GoogleAPIConnection` to wrap all connection shenanigans in `connection.py`

Features:

- [x] Add `GAW_CLIENT_SECRET_FILE_PATH` env variable to allow passing client secret
file path.
- [x] Add `GAW_DISABLE_SSL_CERTS` env variable to allow diasbling ssl certs validation
- [x] Add a vacation responder activation method
- [x] Add a way to view vacation responder in use if any.
- [x] Update README

Features:

- [x] Add `GWA_CA_CERTS_PEM_FILE` env variable to allow passing custom SSL cert
file path
- [x] Update `LICENSE`
- [x] Update `README`
- [x] Add Gmail Api Wrapper Write operations shell

Bugs:

- [x] Get message body from `return message_payload['body']['data']`
when `return message_payload['parts'][0]['body']['data']` returns a `KeyError`
exception

Features:

- [x] Add Circle CI Configs
- [x] Extract base64 message body