check contact list coming out from get_intermolecular_contacts

[mgiulini]

the contacts retrieved from get_intermolecular_contacts seem to differ from those retrieved using mdanalysis + scipy for pdb file 7so9:

7so9_target.pdb.zip

contacts_mda_7so9_target.txt

It seems that the mda list contains [('A', 84, 'B', 266), ('A', 84, 'B', 265)], while fccpy list contains [('A', 85, 'B', 49), ('A', 84, 'B', 48), ('A', 85, 'B', 48)].