added tests for new SeqEdit class
added tests for new SeqEdit class

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