dillon1000/react

More accurately model OptionalMemberExpression

Extends the new modeling of the previous diff to OptionalMemberExpression. In an 
example such as `a?.b?.c`, we now model that not only is the `.c` conditional, 
but our control flow graph accurately reflects the fact that the `.c` is only 
evaluated if `a.b` exists. Previously we knew it was conditional but the CFG 
allowed a path from a being null through to evaluation of `.c`.