Bump RocksDB version to 4.13 (#1405)

Summary:
Bump RocksDB version to 4.13

Test Plan:
unit tests

Reviewers: sdong, IslamAbdelRahman, andrewkr, lightmark

Subscribers: leveldb

HISTORY.md

 # Rocksdb Change Log
-## Unreleased
+## 4.13.0 (10/18/2016)
 ### Public API Change
 * DB::GetOptions() reflect dynamic changed options (i.e. through DB::SetOptions()) and return copy of options instead of reference.
 * Added Statistics::getAndResetTickerCount().
 
 ### New Features
 * Add DB::SetDBOptions() to dynamic change base_background_compactions and max_background_compactions.
-
-### New Features
 * Added Iterator::SeekForPrev(). This new API will seek to the last key that less than or equal to the target key.
 
 ## 4.12.0 (9/12/2016)

include/rocksdb/version.h

@@ -5,7 +5,7 @@
 #pragma once
 
 #define ROCKSDB_MAJOR 4
-#define ROCKSDB_MINOR 12
+#define ROCKSDB_MINOR 13
 #define ROCKSDB_PATCH 0
 
 // Do not use these. We made the mistake of declaring macros starting with