fix bug in PersistentStoreManager.java
Merge branch 'huiyang' of https://github.com/owwlo/web_search_engine_course
Merge branch 'huiyang' of https://github.com/owwlo/web_search_engine_course
Merge branch 'master' of https://github.com/owwlo/web_search_engine_course into huiyang
fix documentTermFrequency in compressed indexer
Merge branch 'master' of https://github.com/owwlo/web_search_engine_course into huiyang
more stopwords; fix Bha