Add Tests for Annotating Hierarchy of ComponentDefinitions

[nroehner]

Add tests for sequences_to_features classes/methods to test_curation.py for annotating a hierarchy of ComponentDefinitions. Test should load SBOL file containing hierarchy of ComponentDefinitions in which both a parent and a child ComponentDefinition contain the same feature to be annotated in their sequences. The test should check whether the feature is annotated in both ComponentDefinitions.