updated explanation to be up-to-date with stats-from-merge-files.pl v 1.17
updated explanation to be up-to-date with stats-from-merge-files.pl v 1.17

mjg17/ensembl,Ensembl/ensembl,willmclaren/ensembl,at7/ensembl,james-monkeyshines/ensembl,mjg17/ensembl,danstaines/ensembl,danstaines/ensembl,at7/ensembl,danstaines/ensembl,muffato/ensembl,mjg17/ensembl,muffato/ensembl,mjg17/ensembl,muffato/ensembl,james-monkeyshines/ensembl,at7/ensembl,james-monkeyshines/ensembl,muffato/ensembl,Ensembl/ensembl,willmclaren/ensembl,james-monkeyshines/ensembl,Ensembl/ensembl,at7/ensembl,Ensembl/ensembl