Don't bail out on processing a class if an error is raised when
determining the parent class name.

instead of "sexp? exp and exp.node_type == :blah"
or "sexp? exp and exp[0] == :blah"

although we're still depending on "globals",
just not ones shared with every Ruby app

fixes most parsing issues, but will use parser
based on Ruby version used to run Brakeman

allowing Brakeman to easily be used as a library now

and methods called outside of controller