difflib_test: add more tests
Here is a partial port of python 3 difflib package. Its main goal was to make available a unified diff implementation, mostly for testing purposes.
The following class and functions have be ported:
SequenceMatcherunified_diff()Related doctests have been ported as well.
I have barely used to code yet so do not consider it being production-ready. The API is likely to evolve too.