Merge branch '#75_bug_fixed' into 'master'

prer-release refactors

See merge request flatland/flatland!90

requirements_continuous_integration.txt

@@ -11,5 +11,6 @@ flake8-eradicate==0.2.0
 twine==1.12.1
 pydeps==1.7.2
 jupyter==1.0.0
+pytest-xvfb==1.2.0
 git+https://github.com/who8mylunch/Jupyter_Canvas_Widget.git@bd151ae1509c50b5809944dd3294f58b7b069c86
 

requirements_dev.txt

@@ -3,7 +3,6 @@ tox==3.5.2
 twine==1.12.1
 pytest==3.8.2
 pytest-runner==4.2
-pytest-xvfb==1.2.0
 numpy==1.16.4
 recordtype==1.3
 xarray==0.11.3