The method length() now throws if end < start and the feature is not on a circular slice, so fix the documentation.
The method length() now throws if end < start and the feature is not on
a circular slice, so fix the documentation.

Also, format method.

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