Database migration to add support for user comments on bounties and private messages between users.
Update user and bounty factories to allow generating comments on creation.
Factories no longer generate random content by default for bounty comments and private messages.
Bounties created when seeding the database now have comments attached.
Allow the properties of child comments on users and bounties to be specified when constructing the user or bounty objects.
The database is now seeded with comments with random content generated by Faker.
Fix logic errors in the vote validator.
If a user account is deleted, all of its votes are deleted as well.
The Bounty factory now takes callbacks for creating its associated objects.
Make bounty names case-insensitively unique.