remove salt, change timestamp

[squirrelo]

Minor tweaks to the database:

• Removed the salt column from users since it is stored in the password hash with bcrypt.
• Changed the processed_data column processed_date to be timestamp instead of date.

[adamrp]

👍

[coveralls]

Coverage remained the same when pulling a18a6e2 on squirrelo:dbfix into c05e85d on biocore:master.