Chartify

------------------

* Added Boxplot Chart including example in examples notebook

------------------

* Fixed a few errors in example and tutorial notebooks
* Fixed a typo in requirements.txt

------------------

* Updated package requirements
* Got rid of future deprecation warnings
* Bugfix related to legend for graphs with multiple groups and colors

------------------

* Support pyyaml 5.2+

------------------

* Reduce dependencies by switching from Jupyter to IPython.

------------------

* Updated Python to 3.6+ and Pandas to 1.0+ (Thanks tomasaschan!)
* Updated Bokeh to 2.0+
* Removed colour dependency to fix setup errors.