Variable for timezone

[Mikkou]

When I got dumps, I see that a name of files consist of incorrect time. It will be better to put correct time to name which getting from a server where I setup this container.

[tiredofit]

Timezone can be set by var TIMEZONE. It's part of the earlier base image https://github.com/tiredofit/docker-alpine/blob/edge/README.md . Also, I'm not doing much updates as you've found to to this repository, I'm working out of https://github.com/tiredofit/docker-db-backup instead :)

[Mikkou]

@tiredofit thanks!