Syllogism demo

Initial pull request for testing syllogisms. Work in progress. Not to be merged yet. Comments welcome.
I know. For the start, I just copy-pasted all the example sentences in their own scm files since we would require their scheme representation for testing. However, since there're so many syllogisms, I concentrated on a few since converting every syllogism into Scheme would not only take a lot of time but for a lot of the others, there would still be a lot of representation issues that would need to be discussed.
Since I started writing the ```load_r2l.py``` module, I'm not sure which course we should take:
1. The first possibility is that we take a Scheme file as input and perform PLN on that as we've done for the Socrates example.
2. The second possibility is that we take a txt file as input, parse the premises with RelEx2Logic and then perform reasoning on the output.
I think we should do the latter since only then we'd have a complete pipeline and the first one requires manually creating the lengthy Scheme representations. However, if doing the latter all necessary modifications would need to be implemented in R2L previously and only then could PLN follow suit. What is your opinion of this, Cosmo?