Fix: ASGI wrapper is not required anymore, causes issues

Fix: AlephApp wrapper was not compatible with Uvicorn

Feature: Allow specifying `ref` in `aleph post` command

Internal: Assert that a has really been returned

Internal: Require latest aleph-message release

Cleanup: Replace dicts with models, strings with enums

Fix: Explitely only support Python 3

Change: Hide CLI subscriptions behind `--beta` argument

Fix: Setup requires underscores in names

Chore: Update aleph-message version requirement