changed add_gene to be add_Gene for consistency with rest of the API
changed add_gene to be add_Gene for consistency with rest of the API

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