add knn_classifier code

Author: pinard.liu

classic-machine-learning/knn_classifier.ipynb

@@ -65,7 +65,7 @@ http://www.cnblogs.com/pinard 刘建平Pinard
 [决策树算法原理(下)](https://www.cnblogs.com/pinard/p/6053344.html)|无
 [scikit-learn决策树算法类库使用小结](https://www.cnblogs.com/pinard/p/6056319.html) |[代码1](https://github.com/ljpzzz/machinelearning/blob/master/classic-machine-learning/decision_tree_classifier.ipynb) [代码2](https://github.com/ljpzzz/machinelearning/blob/master/classic-machine-learning/decision_tree_classifier_1.ipynb)
 [K近邻法(KNN)原理小结](https://www.cnblogs.com/pinard/p/6061661.html) |无
-[scikit-learn K近邻法类库使用小结](https://www.cnblogs.com/pinard/p/6065607.html) |TO be uploaded
+[scikit-learn K近邻法类库使用小结](https://www.cnblogs.com/pinard/p/6065607.html) |[代码](https://github.com/ljpzzz/machinelearning/blob/master/classic-machine-learning/knn_classifier.ipynb
 [朴素贝叶斯算法原理小结](https://www.cnblogs.com/pinard/p/6069267.html) |无
 [scikit-learn 朴素贝叶斯类库使用小结](https://www.cnblogs.com/pinard/p/6074222.html)| TO be uploaded
 [最大熵模型原理小结](https://www.cnblogs.com/pinard/p/6093948.html)|无