Added another argument to fetch_by_region():

    Arg [7]    : boolean $no_fuzz
                 If true, do not use "fuzzy matching" (see below).

  This was done to allow the user to by-pass the fuzzy matching code.
  This will allow for some speed increases and to remove any ambiguity
  around the results from this method.

  Also inserted clarifying comment about stickleback DB ('groups' vs.
  'chromosomes') from Anne.