feat :add kubetnetes docs

how to use ocelot with kubetnetes docs

docs/features/kubernetes.rst

@@ -0,0 +1,56 @@
+Kubernetes
+==============
+
+This feature was requested as part of `Issue 345 <https://github.com/ThreeMammals/Ocelot/issues/345>`_ . to add support for kubernetes's service discovery provider. 
+
+The first thing you need to do is install the NuGet package that provides kubernetes support in Ocelot.
+
+``Install-Package Ocelot.Provider.Kubernetes``
+
+Then add the following to your ConfigureServices method.
+
+.. code-block:: csharp
+
+    s.AddOcelot()
+     .AddKubernetes();
+
+If you have services deployed in kubernetes you will normally use the naming service to access them.
+
+The following example shows how to set up a ReRoute that will work in kubernetes. The most important thing is the ServiceName which is made up of the 
+kubernetes service name. We also need to set up the ServiceDiscoveryProvider in 
+GlobalConfiguration. The example here shows a typical configuration. It assumes kubernetes api server is running on 192.168.0.13 and that the api service is on port 443.
+
+The example below is taken from the samples folder so please check it if this doesnt make sense!
+
+.. code-block:: json
+
+    {
+  "ReRoutes": [
+    {
+      "DownstreamPathTemplate": "/api/values",
+      "DownstreamScheme": "http",
+      "UpstreamPathTemplate": "/values",
+      "ServiceName": "downstreamservice",
+      "UpstreamHttpMethod": [ "Get" ],
+      "QoSOptions": {
+        "ExceptionsAllowedBeforeBreaking": 3,
+        "DurationOfBreak": 10000,
+        "TimeoutValue": 5000
+      },
+      "FileCacheOptions": { "TtlSeconds": 15 }
+    }
+  ],
+  "GlobalConfiguration": {
+    "RequestIdKey": "OcRequestId",
+    "AdministrationPath": "/administration",
+    "ServiceDiscoveryProvider": {
+      "Host": "192.168.0.13",
+      "Port": 443,
+      "Token": "txpc696iUhbVoudg164r93CxDTrKRVWG",
+      "Namespace": "dev",
+      "Type": "kube"
+    }
+  }
+}
+
+There is no way for Ocelot to work these out for you.