Ensure org slug includes root org slug when update
Ensure org slug includes root org slug when update

When updating a display name for an organization, we update the slug
accordingly. However, for organizations that were children of another
organization, we were not appropriately grabbing the root
organization's slug value to prefix to the updated child organization
slug. This patch fixes that.

Fixes Issue #72

jaypipes/procession,jaypipes/procession