Kangas

New in this release:
* Support for colab
* New and updated notebooks
* System doesn't download or unzip files on kg.read\_() methods if not needed
* Switch to DataGrid(filename) rather than DataGrid(filename=filename)
* Docstring updates
* Updated filter expression docs
* Allow PIL images to auto-map to Image asset
* docs cli commands
* Added dg[column_name], and dg.to_dicts(column_names)
* all docstrings added for DataGrid
* Untitled datagrid's save in temp dir

New in this release:
* Fixed two bugs with nulls in groups now that we don't remove them in the GROUP
* continue in loop
* np.array()
* Special case for currency that ends up "" (eg, "$.")
* Added Kangas About dialog
* Added /datagrid/status endpoint
* Fixed dg.info() when there are rows with missing values
* More docstrings

New in this release:
* Pass the protocol to the backend when starting in Python
* Added protocol to DataGrid.show()

Updates in this release:
* Added `--protocol http|https` to `kangas server`
* Fixed a bug in parsing negative numbers in filter expression
* Refinements in starting/stopping servers
* Added missing query params in colab
* Added workaround for old version of PIL on colab

New in this release:
* Refresh Button
* CSS tweaks
* Allow NULL values to be a category in Category charts
* Show Category charts for grouped boolean columns
* Added `kangas server --terminate`
* Fixed encoding error in histogram charts
* add link to kangas github
* Made header so that it stays on screen
* Show None for boolean column values that are NULL
* Added ascending/descending arrow in UI on group and sort
* WIP: colab (not working yet)
* Added tests for dataframes
* Added a slight delay in opening webbrowser
* Re-added StyleEngineProvider to force proper styling on server
* Better dg.head() and .tail() in jupyter
* Added dg.pop(index) for in-memory datagrids

Changes included in this release:

* better filter hint
* fixed reading dataframe
* display grid as HTML with head/tail in jupyter
* better progress info
* fixed error in finding out if servers were running
* removed StyledEngineProvider for now