account for number of lone pairs in isomorphismTest

I forgot to modify the number of lone pairs according to the element.
refactored the hydrogen saturator method in adjlist in its own class

created a class method, rather than an instance method because it
doesn't use any important attributes.
corrected typo in isomorphismTest.py
refactored the consistency checks in adjlist in ConsistencyChecker class

currently 2 checks exists:
1) valency of atom
2) multiplicity must be odd

if not correct, an appropriate error is raised.