added graphviz to install_requires in setup.py
added graphviz to install_requires in setup.py

recski/4lang,kornai/4lang,Eszti/4lang,Eszti/4lang,kornai/4lang,recski/4lang,kornai/4lang,recski/4lang,Eszti/4lang,recski/4lang,Eszti/4lang,kornai/4lang