Remove seed data.

Seed data should be used in production as well as development so this
data really is development data. At the moment it’s another thing to
maintain and another thing that could go wrong stopping people from
contributing to the proejct.
Add account to People
Example Person serializer.

Notice there’s tests too :)
Clean noisy test.
Fix signing up.

This was my bad.
Added webhook storage & signature

A Webhook record is created for each webhook sent out, which stores the
body and other info.  For https://assemblymade.com/helpful/wips/108

The webhook is signed with a HMAC-SHA256 for verification.  Per
https://assemblymade.com/helpful/wips/107

To be accomplished in future WIPs, this commit does not address:

* Viewing the webhook status
* Retrying webhooks
Fixed DB schema sync issue on Message

The 'from' column was removed from Message in a890eadb But the schema
and message model wasn't updated to reflect this.  Tests were still
passing because the schema had the column.  But a full db:migrate:reset
caused it to start failing.

This is the minimum necessary to make it work again.
Merge branch 'master' into add_webhook_storage

Conflicts:
	db/schema.rb
fix after sign in path
removed autotest stuff from gemfile
update getting started instructions
Use fake sidekiq in tests
Re-add mailman script