[Tests] Clean tests
the abseil testing library (https://abseil.io/docs/python/quickstart.html) is better than the one I had before, so I decided to switch to that and changed the `setup.py` config file. 
Abseil has more support and a cleaner API for parametrized testing I think. 

I added a list of all dataset scripts that are currently on AWS, but will replace that once the 
API is integrated into this lib. 

One can now easily test for just a single function for a single dataset with:
`tests/test_dataset_common.py::DatasetTest::test_load_dataset_wikipedia` 

NOTE: This PR is rebased on PR #29 so should be merged after.