Add RavenDB on README.MD

Author: furlaneto

README.md

@@ -15,5 +15,6 @@ Diana is a flexible and extensible API to connect NoSQL databases. It brings an
 * **Hbase**: HBase is an open source, non-relational, distributed database modeled after Google's BigTable and is written in Java. It is developed as part of Apache Software Foundation's Apache Hadoop project and runs on top of HDFS (Hadoop Distributed File System), providing BigTable-like capabilities for Hadoop. That is, it provides a fault-tolerant way of storing large quantities of sparse data (small amounts of information caught within a large collection of empty or unimportant data, such as finding the 50 largest items in a group of 2 billion records, or finding the non-zero items representing less than 0.1% of a huge collection).
 * **Mongodb**: MongoDB is a free and open-source cross-platform document-oriented database program. Classified as a NoSQL database program, MongoDB uses JSON-like documents with schemas.
 * **Orientdb**: OrientDB is an open source NoSQL database management system written in Java. It is a multi-model database, supporting graph, document, key/value, and object models, but the relationships are managed as in graph databases with direct connections between records. It supports schema-less, schema-full and schema-mixed modes. It has a strong security profiling system based on users and roles and supports querying with Gremlin along with SQL extended for graph traversal. OrientDB uses several indexing mechanisms based on B-tree and Extendible hashing, the last one is known as "hash index", there are plans to implement LSM-tree and Fractal tree index based indexes. Each record has Surrogate key which indicates position of record inside of Array list , links between records are stored either as single value of record's position stored inside of referrer or as B-tree of record positions (so-called record IDs or RIDs) which allows fast traversal (with O(1) complexity) of one-to-many relationships and fast addition/removal of new links. OrientDB is the second most popular graph database according to the DB-Engines graph database ranking
+* **RavenDB**: RavenDB is an open source document-oriented NoSQL designed, based on .NET/Windows platform. Supports multiple databases and can easily handle hundreds/thousands of databases on the same instance and was designed with multi-tenancy. RavenDB uses JSON (JavaScript Object Notation) to store documents.
 * **Redis**: Redis is a software project that implements data structure servers. It is open-source, networked, in-memory, and stores keys with optional durability.
 * **Riak**: Riak (pronounced "ree-ack" ) is a distributed NoSQL key-value data store that offers high availability, fault tolerance, operational simplicity, and scalability. In addition to the open-source version, it comes in a supported enterprise version and a cloud storage version. Riak implements the principles from Amazon's Dynamo paper with heavy influence from the CAP Theorem. Written in Erlang, Riak has fault tolerance data replication and automatic data distribution across the cluster for performance and resilience.