v0.3.11 release

Features:
* Traffic light overview (#62)

Documentation:
* Downloads badge readme
* List talks and articles in readme (#66)
* Add image to README.rst (#64)

Other improvements:
* Change notebook testing to pytest-notebook (previously these tests were skipped in CI). Add try-except ImportError for pyspark code. (#67)
* Fix a few typo's
* suppress "matplotlib backend" verbose warning
* click on "popmon report" also scrolls to top
* Update HTML reports using Github Actions (#63)
* Bugfix in hist.py that broke the advanced tutorial.

Notebooks:
* Add %%capture to pip install inside of notebooks.
* Make package install in notebooks work with paths with spaces.
* Pickle doesn't work with tests (not really a popmon-specific feature anyway). Changed the notebook to fix the issue, left the code for reference.

* Version bump

v0.3.12 release

* Pin histogram version

* Initialize spark with both histogrammar jar files

Co-authored-by: Max Baak <maxbaak@gmail.com>