DocumentKeyNotFound message now says "NOT found"
Merge pull request #136 from jozic/fix-DKNF-exception-message

DocumentKeyNotFound message now says "NOT found"
Cursor.enumerate(): fix bug on empty cursors.
Merge branch 'master' of https://github.com/ReactiveMongo/ReactiveMongo into prismic

* 'master' of https://github.com/ReactiveMongo/ReactiveMongo:
  Cursor.enumerate(): fix bug on empty cursors.
  DocumentKeyNotFound message now says "NOT found"