Update JAVA-HISTORY.md for v3.13

Summary: Update JAVA-HISTORY.md for v3.13

Test Plan: no code change.

Reviewers: igor, anthony, IslamAbdelRahman, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D43539

java/HISTORY-JAVA.md

@@ -1,5 +1,11 @@
 # RocksJava Change Log
 
+## 3.13 (8/4/2015)
+### New Features
+* Exposed BackupEngine API.
+* Added CappedPrefixExtractor support.  To use such extractor, simply call useCappedPrefixExtractor in either Options or ColumnFamilyOptions.
+* Added RemoveEmptyValueCompactionFilter.
+
 ## 3.10.0 (3/24/2015)
 ### New Features
 * Added compression per level API.