Fixed #6320 -- Clarified a few issues in the contribution docs surrounding the...

Fixed #6320 -- Clarified a few issues in the contribution docs surrounding the triage process. Thanks to telenieko, Edgars Jekabsons and Marc Fargas for their input.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@7632 bcc190cf-cafb-0310-a4f2-bffc1f526a37