Add `LOWER()` when comparing email 

Add LOWER() to the following places:
[Place Number 1](https://github.com/Dewberry/s3api/blob/9b8b15006e92b9689d20fd78884262b94de39bf3/auth/database.go#L75
)
[Place Number 2](https://github.com/Dewberry/s3api/blob/9b8b15006e92b9689d20fd78884262b94de39bf3/auth/database.go#L112
)
