Merge branch 'graphviz' into 'master'

Add graphviz to interactive (it's require in first tutorial)

See merge request !153

setup.py

@@ -112,7 +112,7 @@ setup(name='pystencils',
           'opencl': ['pyopencl'],
           'alltrafos': ['islpy', 'py-cpuinfo'],
           'bench_db': ['blitzdb', 'pymongo', 'pandas'],
-          'interactive': ['matplotlib', 'ipy_table', 'imageio', 'jupyter', 'pyevtk', 'rich'],
+          'interactive': ['matplotlib', 'ipy_table', 'imageio', 'jupyter', 'pyevtk', 'rich', 'graphviz'],
           'autodiff': ['pystencils-autodiff'],
           'doc': ['sphinx', 'sphinx_rtd_theme', 'nbsphinx',
                   'sphinxcontrib-bibtex', 'sphinx_autodoc_typehints', 'pandoc'],