Return tzdata package

`tzdata` package is required by Rails and Django farameworks
Please, don't make too many developers extend postgres image!

P.S. It was removed in: https://github.com/docker-library/postgres/commit/797fadcad2239919ea98aa7a3d14d32b4e8fc525
P.S. And community already start to requested it https://github.com/docker-library/postgres/pull/226 https://github.com/docker-library/postgres/issues/220