resolve "remove seeds" (#64)
- motivation: seeder phone numbers for local dev environment are counterproductive. when two developers both try to run them, they will introduce a tug-of-war over who has registered the signal number. whenever one has registered it, the other will not be able to use it
Removing from blackbox: app/db/seeders/20190125203925-testing-channels.js
Closes #64 (closed)