Remove story.Category

[MehdiK]

Check out #69 for more details. I split this into its own issue as I want this removed as part of V4. The rest, which are non-breaking, can be added at a later time.

[JakeGinnivan]

Maybe this should be renamed rather than removed.

It is really reportFilename?

[MehdiK]

It's basically what we're changing to Tags. Currently it's broken and not used at all as it's overwritten on every BDDfy call!! This is not related to reportFileName. That can be set using the report configuration.