Allow configuration on command line

[AxeOfMen]

Is your feature request related to a problem? Please describe.
It is cumbersome to use multiple configuration files. Depending on the environment, the current working directory may be different. This requires me to create multiple configuration files just to set the migrationsDir setting.

Describe the solution you'd like
I would like to be able to set the migrationsDir configuration on the command line, e.g.

migrate-mongo create my_new_migration_file --migrationsdir ./data/migrations

Ideally other settings would be configurable on the command line as well.

Describe alternatives you've considered
The only alternative I'm aware of is using multiple configuration files

[theogravity]

If you want to create a PR for this, go for it, but it's not something on my list I personally want to write myself.