#15: copied in natural deduction rules from James's Logic class.
So we can discuss which of them we allow for fallacy pattern matching
#15: added a slide set containing the 'monkey's uncle rule'
#15: made the logical expressions in the comments exactly as the ones in the code
(some brackets were missing)
#15 satisfied all tests with new pattern matching approach
as discussed in #15
#15: extracted common part of all fallacy functions in helper function.
Closes #15.