[CONFIG] [SCHEMA]

Summary:
Since we're now running migrations, we need to make sure alembic always knows where it is in the history by "stamping" the revision. This is saved in the `alembic_revision` table in the inbox databasel

You need to do two things to update your working copy for this patch:

1. Add this line to your config.cfg:

`ALEMBIC_INI = ./alembic.ini`

2. Run this in the top-level folder

`alembic stamp head`

This will "stamp" your database to the latest alembic revision hash (should be `269247bc37d3`), meaning that when you run `alembic upgrade head`, it will only apply new migrations. If you don't do this, alembic will try to run _all_ the migrations, even for those whose changes have already been propagated to the relevant database models.

I've also added a script that does this when the database is created, so you don't need to manually do this when booting a new dev box.

(Obviously we should do something different for prod deployments on ec2.)

Test Plan: Running `sudo python tools/create_db.py` should be idempotent, and detect that the database has both already been created and stamped. If not, it will create the DB and stamp it.

Reviewers: spang

Reviewed By: spang

Differential Revision: https://review.inboxapp.com/D24