Set up alembic, and more

- Setup alembic and generate the initial migration
- Add poethepoet to dev dependencies in order to put hard-to-remember
  commands beneath the poetry namespace
- Add psycopg2-binary dependency, for use with postgresql
- Remove dotenv dependency, as it is no longer required
- Add `config.toml` to gitignore. This is because alembic has no
  argument parser that will let you specify the config file to use.
  Developers are encouraged to use `config.toml`, which will be
  automatically recognized, unless they want to implement the argument
  parser functionality for alembic.

.gitignore

@@ -20,4 +20,6 @@ venv.bak/
 
 dist/
 
-result
+result
+
+config.toml