[enhancement] Some suggestions

Dear @mnick ,

i really appriciate this package. However, it is somewhat difficult to fully wrap my head arround it. It would help if you could:

Create an example that solves a classic machine learning problem with sckit-kge, as it is commonly done.
create a detailed documentation of all available algorithms and other functions
explain more about the negative sampling you are talking about in the readme file.
explain how to access the embeddings
maybe support RDF Graph input
make scikit-kge available at pypi

Best regards Chris

mnick / scikit-kge