Refactor to module layout

[campb303]

• Refactored to package layout:

webqueue2api
├── __init__.py
├── api
│   ├── __init__.py
│   ├── app.py
│   ├── auth.py
│   ├── config.py
│   └── resources
│       ├── __init__.py
│       ├── item.py
│       ├── login.py
│       ├── queue.py
│       ├── queue_list.py
│       └── refresh_access_token.py
├── config.py
└── parser
    ├── __init__.py
    ├── config.py
    ├── errors.py
    ├── item.py
    └── queue.py

• Centralized configuration management following a pattern of each package having its own config.py and the top level package has a composite config consisting of the other configurations. Example:

>>> import webqueue2api
>>> webqueue2api.config.parser.environment
"prod"
>>> webqueue2api.config.api.jwt_secret_key
"5wA!*6foTML^EF"
>>> webqueue2api.config.queue_directory = "/path/to/queues"
>>> webqueue2api.config.queue_directory
"/path/to/queues"

• Added WSGI app export easy gunicorn support:

# Starts multi-threaded API server on localhost:8000
gunicorn webqueue2api.api:app
# Authenticate against API
curl -X POST \
    -H "Content-Type: application/json" \
    -d '{"username": "bob", "password": "super_secret"}'

• Added custom errors to parser sub-package
• Updated return codes for API (ex: return 404 when FileNotFoundError is raised)
• Refactored to snake_case
• Reimplemented headers_only loading and json_data serialization