[#77] Add tanker callbacks to guide_step
[#77] Run migration to remove status from article.
[#77] Unpublished search results filtered at a higher level.
[#77] Refactor article callbacks into RailsNlp module.

* qm_after_create et al have been renamed to better reveal intention.
* Re-indexing has a lower priority than analysing, so happens after.
[#77] Update rake admin:analysmodels task to use new module.