This commit aims to fix tests which fails on not finding columns such as
`expireson`. Adding the underscore that are used when creating the table
should fix this.
An issue with this is that it must have worked previously without underscores.
In that case this might break existing usage.
- Call defer store.StopCleanup(store.Cleanup(time.Minute * 5)) after store creation.
- Does not break the existing API (optional, but recommended)
- Based on https://github.com/yosssi/boltstore/reaper
- Deletes expired sessions (where expireson > now())
- Includes tests