remove old commented tabix methods, add support for sereal cache files
remove old commented tabix methods, add support for sereal cache files

Ensembl/ensembl-variation,willmclaren/ensembl-variation,Ensembl/ensembl-variation,Ensembl/ensembl-variation,Ensembl/ensembl-variation,willmclaren/ensembl-variation,willmclaren/ensembl-variation,Ensembl/ensembl-variation,willmclaren/ensembl-variation,willmclaren/ensembl-variation