Update README.md

Author: nlpyang

README.md

@@ -60,6 +60,9 @@ Results on CNN/DailyMail (20/8/2019):
 
 **Package Requirements**: torch==1.1.0 pytorch_transformers tensorboardX multiprocess pyrouge
 
+**Updates**: For encoding a text longer than 512 tokens, for example 800. Set max_pos to 800 during both preprocessing and training.
+
+
 Some codes are borrowed from ONMT(https://github.com/OpenNMT/OpenNMT-py)
 
 ## Trained Models