Renames ARM-8 and ARM-9 to reflect the changed scope

- ARM-8 will continue to describe the end-stage implementation
  of the binding system
- ARM-9 is resurrected from 'withdrawn' (actually 'never written')
  to describe the focused problem of providing hiera data in
  modules, which would be the first-step implementation towards
  ARM-8.
Missing comma on arm-8 metadata
Merge pull request #57 from ahpook/master

Renames ARM-8 and ARM-9 to better reflect their scope