countdownlatch 이용.
Merge branch 'master' of
https://github.com/fastcatsearch/fastcatsearch.git

Conflicts:
	server/src/main/java/org/fastcatsearch/ir/AbstractCollectionIndexer2.java
Merge branch 'master' of https://github.com/fastcatsearch/fastcatsearch.git
문서수가 스레드수보다 적을경우 발생하는 오류 수정
Merge branch 'master' of https://github.com/fastcatsearch/fastcatsearch.git