ENSCORESW-1121: remove bad method
ensure that even for slices with no features, the adaptor bind params are left clean and empty once the method completes
Merge pull request #38 from danstaines/hotfix/get_by_slice

fix for _get_by_slice on feature-less slices
not all gff features are Ensembl Features
changed attributes to use correct casing as per http://gmod.org/wiki/GFF3. Extended testcase to include transcript to test Parent attribute