base.Sequence major cleanup * moved base.Sequence.secstr_has to pdb (it appears that secondary structure it uses is from PDB, which is not a nice thing to do; secondary structure is an entity in itself and must have same names across different sources) * removed stupid base.Sequence.monomers, since base.Sequence is subclass of list * removed all methods that reimplement list behaviour * fixed headers of base.Sequence.from_slice