Add optional validation of filenames and option to run only migrations before a certain date string

[nholmes3]

Is it possible to add an option to validate that the migration files being run are, in fact, prefixed by a date string? The idea behind this is to make sure that migrations do not accidentally run out of order if a developer creates a migration file that is not prefixed by a date string. Current behavior will run any migration files regardless of their name

This validation would also assist with a feature that allows for migrations before a specific date to be run. Something along the lines of migrate-mongo up --before {date} --validate

--validate would throw an error if there are migration files that do not contain a date string prefix
--before {date} will run only migrations that precede the date specified

Let me know if this is something you'd consider adding, and I would be happy to assist in creating the pull request