Added beginner friendly example of diabetes dataset

[aiwithqasim]

Worked on PIMA India's Diabetes dataset using TensorFlow's Decision Forest (TF-DF) & compare the result with Decision Tree that I had did previously.

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[aiwithqasim]

Signed a Contributor License Agreement (CLA).

[aiwithqasim]

@googlebot I signed it!

[achoum]

Hi Qasim, Thanks for the example. It looks great.

[aiwithqasim]

@rstz updated according to the suggested possible improvements. Let me know if still need any improvement. You can give me more ideas. I'll be happy to contribute.

[rstz]

LGTM, Thank you for the revisions. I think we can merge this, and feel free to have a look at GBT models as well.

[aiwithqasim]

@rstz looking forward to it.