Arg [1]       : Bio::EnsEMBL::Gene gene
  Example       : if ($geneA->equals($geneB)) { ... }
  Description   : Compares two genes for equality.
                  The test for eqality goes through the following list
                  and terminates at the first true match:

                  1. If Bio::EnsEMBL::Feature::equals() returns false,
                     then the genes are *not* equal.
                  2. If the biotypes differ, then the genes are *not*
                     equal.
                  3. If both genes have stable IDs: if these are the
                     same, the genes are equal, otherwise not.
                  4. If both genes have the same number of transcripts
                     and if these are (when compared pair-wise sorted by
                     start-position and length) the same, then they are
                     equal, otherwise not.

  Return type   : Boolean (0, 1)

  Exceptions    : Thrown if a non-gene is passed as the argument.