Add tests for compression_ratio property of Array class.
Add tests for compression_ratio property of Array class.

jack-pappas/PyTables,mohamed-ali/PyTables,jennolsen84/PyTables,rabernat/PyTables,jack-pappas/PyTables,andreabedini/PyTables,FrancescAlted/PyTables,dotsdl/PyTables,jack-pappas/PyTables,joonro/PyTables,dotsdl/PyTables,cpcloud/PyTables,mohamed-ali/PyTables,andreabedini/PyTables,joonro/PyTables,avalentino/PyTables,mohamed-ali/PyTables,cpcloud/PyTables,jennolsen84/PyTables,joonro/PyTables,dotsdl/PyTables,jennolsen84/PyTables,gdementen/PyTables,avalentino/PyTables,jack-pappas/PyTables,rabernat/PyTables,cpcloud/PyTables,jack-pappas/PyTables,rdhyee/PyTables,rabernat/PyTables,andreabedini/PyTables,gdementen/PyTables,rdhyee/PyTables,jennolsen84/PyTables,joonro/PyTables,gdementen/PyTables,PyTables/PyTables,PyTables/PyTables,andreabedini/PyTables,tp199911/PyTables,tp199911/PyTables,cpcloud/PyTables,tp199911/PyTables,FrancescAlted/PyTables,rabernat/PyTables,PyTables/PyTables,tp199911/PyTables,mohamed-ali/PyTables,avalentino/PyTables,rdhyee/PyTables,gdementen/PyTables,FrancescAlted/PyTables,dotsdl/PyTables,rdhyee/PyTables