Autoexpose tasks, no need to run luigi.expose any longer

Change-Id: I16fde24982a49163497d47091e972e1dde85368d
Reviewed-on: https://gerrit.spotify.net/gerrit/34706
TC-Compile-And-Test: teamcity teamcity <teamcity@spotify.com>
Reviewed-by: Elias Freider <freider@spotify.com>