Always read article metadata from master branch to prevent missing metadata
Always read article metadata from master branch to prevent missing metadata

- This fixes #25.

- There was an issue where we would not save the meta data to branched
  articles.  The scenario was the following:
    - User is branching an article and they already have a branch created on
      github
    - We read the SHA of the article they are branching and save the article
      edits to the existing branch.  However, we don't ever go back and save
      the metadata for the branched article.  So, reading the branch version of
      the article would always fail since it had no metadata.
- Solution is to save us the trouble and never read metadata from branches.
  This makes sense because we never save changes to metadata on branches
  anyway.

paulocheque/guides-cms,pluralsight/guides-cms,paulocheque/guides-cms,paulocheque/guides-cms,pluralsight/guides-cms,pluralsight/guides-cms