In flask's development server, the route handlers
run in a different thread than the main thread
thus an in-memory database created in the main thread
cannot be acccessed by the route handlers.
Switching the default database location to a temporary
file solves the isssue.
See full explanation here:
https://gehrcke.de/2015/05/in-memory-sqlite-database-and-flask-a-threading-trap/
* Use absolute imports and rename package to ihatemoney
* Add a ihatemoney command
* Factorize application creation logic
* Refactor the tests
* Update the wsgi.py module with the new create_app() function
* Fix some styling thanks to Flake8.
* Automate Flake8 check in the CI.
