fix: install tzdata in docker

[lksv]

fixes the error

error: could not load time location: unknown time zone Europe/Prague in line 0: SHOW TABLES FROM "omega" LIKE 'schema_migrations'

This error was discussed also in #494 and #201 but not solved.

[coveralls]

coverage: 59.226%. remained the same
when pulling f30163a on lksv:patch-1
into a5dc5d1 on golang-migrate:master.

[dhui]

Thanks for looking at other past issues!
This still has the stale tz data problem and we prefer to fail loudly instead of silently introduce bugs