Replace pipenv with poetry

Also make the images in the notebook a bit smaller

requirements.txt

@@ -0,0 +1,53 @@
+attrs==19.2.0
+backcall==0.1.0
+bleach==3.1.0
+cycler==0.10.0
+decorator==4.4.0
+defusedxml==0.6.0
+entrypoints==0.3
+ipykernel==5.1.2
+ipython==7.8.0
+ipython-genutils==0.2.0
+ipywidgets==7.5.1
+jedi==0.15.1
+Jinja2==2.10.1
+joblib==0.14.0
+jsonschema==3.0.2
+jupyter==1.0.0
+jupyter-client==5.3.3
+jupyter-console==6.0.0
+jupyter-core==4.5.0
+kiwisolver==1.1.0
+MarkupSafe==1.1.1
+matplotlib==3.1.1
+mistune==0.8.4
+nbconvert==5.6.0
+nbformat==4.4.0
+notebook==6.0.1
+numpy==1.17.2
+pandas==0.25.1
+pandocfilters==1.4.2
+parso==0.5.1
+pexpect==4.7.0
+pickleshare==0.7.5
+prometheus-client==0.7.1
+prompt-toolkit==2.0.9
+ptyprocess==0.6.0
+Pygments==2.4.2
+pyparsing==2.4.2
+pyrsistent==0.15.4
+python-dateutil==2.8.0
+pytz==2019.2
+pyzmq==18.1.0
+qtconsole==4.5.5
+scikit-learn==0.21.3
+scipy==1.3.1
+Send2Trash==1.5.0
+six==1.12.0
+terminado==0.8.2
+testpath==0.4.2
+tornado==6.0.3
+traitlets==4.3.2
+wcwidth==0.1.7
+webencodings==0.5.1
+widgetsnbextension==3.5.1