Fixed a comment in the ResidueContainer.__repr__() method.
Updated the MoleculeContainer.__repr__() method.
The ResidueList add_item() method now calls the is_empty() method.
The SpinList add_item() method now uses the is_empty() method.
Created the ResidueList.is_empty() method.
Created the SpinList.is_empty() method.
Created the ResidueContainer.is_empty() method.
Improvements to the ResidueContainer.__repr__() method.
Comment fix in the SpinList.add_item() method.
Fixes for the SpinContainer.__repr__() method.
This method was fubar!