Implement + unit test explore_clustering

[lephanthuymai]

Hi Aditya et. al, Please help to review my PR with changes below:

• Implement and write unit tests for explore_clustering
• Implement and write unit tests for explore_KMeans_clustering
• Implement and write unit tests for explore_DBSCAN_clustering
• Create eda_playround.ipynb to give an example of how we use the functions for EDA tasks on a dataset

I have run all the tests locally, they all passed.

Notes:

• I'm using menus.csv as the test dataset, there are numeric, categorical and text columns, should be fine to utilize all of our EDA functions
• There are issues with testing matplotlib plots, I have to use matplotlib.use("Agg") to disable opening plot windows in the test file, it causes some texts not generated for the plot objects, hence I can only do some simple tests for these plots. There are some other ideas for testing this kind of plot: https://stackoverflow.com/questions/27948126/how-can-i-write-unit-tests-against-code-that-uses-matplotlib, which I find quite complex. If you have better ideas on how to test them, please let me know.

Thanks.

[lephanthuymai]

Hi @adibns , After some discussions with Tiff, Peter (TA), and Varada, I have updated the unit tests for verifying plots. The tests passed and the EDA notebook renders fine. Sorry that it will take you some time to review my commits again. Thank you for your help. Best, Mai