Update README.md (#181)

README.md

@@ -17,7 +17,7 @@
 
 Fresh approach to Machine Learning in PHP. Algorithms, Cross Validation, Neural Network, Preprocessing, Feature Extraction and much more in one library.
 
-PHP-ML requires PHP >= 7.0.
+PHP-ML requires PHP >= 7.1.
 
 Simple example of classification:
 ```php