added tests on stable id event for a given archive stable id and stable id also updated existing tests to use is rather than ok whenever possible
added tests on stable id event for a given archive stable id and stable id
also updated existing tests to use is rather than ok whenever possible

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