adding readme.md

Change-Id: Ib802a5b1b9fd013b89153731e23930ad724f7ad5

+onos : Open Network Operating System 
+====================================
+
+### What is ONOS?
+ONOS is a new SDN network operating system designed for high availability, performance, scale-out. 
+
+### Top-Level Features
+
+* High availability through clustering and distributed state management.
+* Scalability through clustering and sharding of network device control.
+* Performance that is good for a first release, and which has an architecture that will continue to support improvements.
+* Northbound abstractions for a global network view, network graph, and application intents.
+* Pluggable southbound for support of OpenFlow and new or legacy protocols.
+* Graphical user interface to view multi-layer topologies and inspect elements of the topology.
+* REST API for access to Northbound abstractions as well as CLI commands.
+* CLI for debugging.
+* Support for both proactive and reactive flow setup.
+* SDN-IP application to support interworking with traditional IP networks controlled by distributed routing protocols like BGP.
+* IP-Optical use case demonstration.
+
+Checkout out our [website](http://www.onosproject.org) and our [tools](http://onos.staging.wpengine.com/software/#tools)