* add version-space learner + small fix

* add test for version-space learner + trivial example

* Update README.md

* fix small bug in knowledge.py

If hypotheses was empty, it would fail.

* add knowledge.ipynb

* fix dollar signs

* add image

* Update README.md

* add powerset to utils

* add powerset test

* Create knowledge.py

* Create test_knowledge.py

* add header docstring to knowledge.py

* update learning docstring

* minor edits in knowledge.py