Read database passwords from my.cnf, .pgpass file or other stand

It would be great if instead of having to set ENV variables, db-migrate would look into the standard password files (my.cnf for MySQL and .pgpass for PostgreSQL) similar to how Sqitch handles this: https://github.com/theory/sqitch/blob/master/lib/sqitch-passwords.pod#user-content-Use_a_Password_File
##

---
Want to back this issue? **[Post a bounty on it!](https://www.bountysource.com/issues/26803935-read-database-passwords-from-my-cnf-pgpass-file-or-other-stand?utm_campaign=plugin&utm_content=tracker%2F73887&utm_medium=issues&utm_source=github)** We accept bounties via [Bountysource](https://www.bountysource.com/?utm_campaign=plugin&utm_content=tracker%2F73887&utm_medium=issues&utm_source=github).