Notes section is really a Status section

* Rename the "Notes" section as "Status".
* Remove the emphasis from the entire section and
  place emphasis on the "work in progress" sentence.
* Call out that the spec is not stable.
* Rework paragraph about contributing.
* Tweak some grammar and punctuation (take the commas 
  from over here and push them over there -- Patrick).
Merge pull request #37 from reinh/patch-1

Notes section is really a Status section