Update README.md

Author: tirthajyoti

README.md

@@ -11,7 +11,7 @@ Essential codes for jump-starting machine learning/data science with Python
 * _k_-nearest neighbor classification
 * Decision trees and Random Forest
 * Support vector machine classification
-* K-means clustering
+* _K_-means clustering
 
 ### Function approximation by linear model and Deep Learning
 * Demo notebook to illustrate the superiority of deep neural network for complex nonlinear function approximation task.