Added functionality to rescue from flows that fuck up.

Changes
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* Added #rescue_from into class_methods
* inputed begin rescue end into run_next which is the core method used by cascadence
  to run the flow into the next state
* created 1 new test to make sure this stuff works
Built in the ability to rescue from a flow

Changes
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* Added ::collect_superclasses to helper which provides a way
  to extract all the superclasses from given a class
* Added rescuers to the run_next loop
* Added tests for inheriting rescue loops and and whatnot
* added tests for collect_superclasses
* Removed rspec mocks because they would periodically cause stack-frame errors

Side-Effects
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* Runner specs no longer actually proveably test that #call was invoked...
  but I guess I just sort of take it on faith that it is