Update CI tests, update version

Author: Jürgen Hasch

.bumpversion.cfg

@@ -1,5 +1,5 @@
 [bumpversion]
-current_version = 0.5.0
+current_version = 0.5.3
 commit = True
 message = release {new_version}
 tag = False

tox.ini

@@ -6,7 +6,7 @@ envlist =
     clean,
     check,
     lint,
-    {py36,py37,py38}-notebook{55,60},
+    {py36,py37,py38}-notebook{60,63},
     report,
 
 [testenv]
@@ -15,7 +15,7 @@ basepython =
     py36: {env:TOXPYTHON:python3.6}
     py37: {env:TOXPYTHON:python3.7}
     py38: {env:TOXPYTHON:python3.8}
-    {spell}: {env:TOXPYTHON:python3.6}
+    {spell}: {env:TOXPYTHON:python3.8}
     {appveyorartifacts,lint,check}: {env:TOXPYTHON:python3}
     {condarecipe}: {env:TOXPYTHON:python3}
     {clean,codecov,coveralls,report}: {env:TOXPYTHON:python3}
@@ -32,8 +32,8 @@ deps =
     jupyter_latex_envs>=1.4.0
     mock
     nose
-    notebook55: https://github.com/jupyter/notebook/archive/5.5.0.zip
     notebook60: https://github.com/jupyter/notebook/archive/6.0.0.zip
+    notebook63: https://github.com/jupyter/notebook/archive/6.3.0.zip
     notebookmaster: https://github.com/jupyter/notebook/archive/master.zip
     notebook: notebook
 commands =