add link to Kaggle blog post

Author: justmarkham

pml.md

@@ -11,3 +11,7 @@ permalink: /pml/
 ## Supplementary Videos
 
 - [Video lectures from "An Introduction to Statistical Learning"](http://www.dataschool.io/15-hours-of-expert-machine-learning-videos/): Videos for Chapters 4, 5, 6, 8, and 10 can help to deepen your understanding of the topics presented in this course.
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+## Machine Learning Competitions
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+- [Participating in Kaggle's Allstate Purchase Prediction Challenge](http://www.dataschool.io/kaggle-allstate-purchase-prediction-challenge/): Description of what it's like to compete in a Kaggle competition, including links to a project paper, R code, presentation slides, and a presentation video.