Add MetaDatum::People model, factory and specs

Squashed commit of the following:

commit a4d9005f5b263dd745977a8c852e886dae56f028
Author: Thomas Schank <DrTom@schank.ch>
Date:   Wed Dec 17 13:41:13 2014 +0100

    ... do the rubocop thing ...

commit 9c2c06fafe8d4a62c81dbe7ba3cc3cfa410466c2
Author: Thomas Schank <DrTom@schank.ch>
Date:   Wed Dec 17 13:33:54 2014 +0100

    ... update cider-ci tasks  ...

commit eaaad9e010c04eabe023ec5027da12577d3732ae
Author: Thomas Schank <DrTom@schank.ch>
Date:   Wed Dec 17 13:32:50 2014 +0100

    ... specing out ...

commit cd4bff7de77e5a73181d441c8c2acdb983f178bb
Author: Thomas Schank <DrTom@schank.ch>
Date:   Wed Dec 17 12:50:08 2014 +0100

    start ...
Improving MetaDatum::People specs
Add MetaDatum::Users model, factory and specs

Squashed commit of the following:

commit e6c68269a8d7f708e7415862e16d1ff4946b449f
Author: Thomas Schank <DrTom@schank.ch>
Date:   Wed Dec 17 15:12:42 2014 +0100

    Minor fixes

commit 7279f91e02cacae941674a91d5066154865b2e00
Author: Thomas Schank <DrTom@schank.ch>
Date:   Wed Dec 17 15:05:29 2014 +0100

    spec fix syntax

commit 602f4690f2e39760149a02c7c2612a194b3383ec
Author: Thomas Schank <DrTom@schank.ch>
Date:   Wed Dec 17 15:03:35 2014 +0100

    introduce meta_datum_users ...
extract 'living styleguide' builder into module

also add a unit test
cider conf: whitespace
cider conf: add styleguide-conformity_defaults
add HAML-Lint (gem, config file, cider spec)
styleguide: add test, fix errors (generate references)