Add Cloudera's blog post to USERS.md

Summary: As title

Test Plan: none

Reviewers: yhchiang, rven, anthony, IslamAbdelRahman, kradhakrishnan, sdong

Reviewed By: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D46053

USERS.md

@@ -34,3 +34,6 @@ Tango is using RocksDB as a graph storage to store all users' connection data an
 ## Turn
 Turn is using RocksDB as a storage layer for their key/value store, serving at peak 2.4MM QPS out of different datacenters.
 Check out our RocksDB Protobuf merge operator at: https://github.com/vladb38/rocksdb_protobuf
+
+## Santanader UK/Cloudera Profession Services
+Check out their blog post: http://blog.cloudera.com/blog/2015/08/inside-santanders-near-real-time-data-ingest-architecture/