Down migrations with mongodb

[fleg]

Down migrations are NOT run in reverse run order with mongodb driver

example:

fleg@fleg-pc:~$ db-migrate up
[INFO] Processed migration 20150312073909-users
[INFO] Processed migration 20150312074623-users-populate
[INFO] Processed migration 20150312080314-users-populate-2
[INFO] Done

fleg@fleg-pc:~$ db-migrate down -c 3
[INFO] Processed migration 20150312073909-users
[INFO] Processed migration 20150312074623-users-populate
[INFO] Processed migration 20150312080314-users-populate-2
[INFO] Done

Probably because of missing sorting by run_on field in allLoadedMigrations function

[wzrdtales]

@fleg Bugfix published in v0.9.9.

Thank you for reporting