kubernetes provider (#772)

* feat: Kubernetes ServiceDiscoveryProvider

* 编写k8s测试例子

* feat：fix kube config

* feat： remove port

* feat ： complete the k8s test

* feat :  add kubeserviceDiscovery test

* feat : add kube provider unittest

* feat :add kubetnetes docs

how to use ocelot with kubetnetes docs

* keep the configuration as simple as possible, no qos, no cache

* fix: use http

* add PollingKubeServiceDiscovery

* feat : refactor logger

* feat : add  pollkube docs

* feat：Remove unnecessary code

* feat ： code-block json

test/Ocelot.UnitTests/Kubernetes/KubeProviderFactoryTests.cs

@@ -0,0 +1,35 @@
+using Microsoft.Extensions.DependencyInjection;
+using Moq;
+using Ocelot.Configuration;
+using Ocelot.Logging;
+using Ocelot.Provider.Kubernetes;
+using Shouldly;
+using System;
+using Xunit;
+
+namespace Ocelot.UnitTests.Kubernetes
+{
+    public class KubeProviderFactoryTests
+    {
+        private readonly IServiceProvider _provider;
+
+        public KubeProviderFactoryTests()
+        {
+            var services = new ServiceCollection();
+            var loggerFactory = new Mock<IOcelotLoggerFactory>();
+            var logger = new Mock<IOcelotLogger>();
+            loggerFactory.Setup(x => x.CreateLogger<Kube>()).Returns(logger.Object);
+            var kubeFactory = new Mock<IKubeApiClientFactory>();
+            services.AddSingleton(kubeFactory.Object);
+            services.AddSingleton(loggerFactory.Object);
+            _provider = services.BuildServiceProvider();
+        }
+
+        [Fact]
+        public void should_return_KubeServiceDiscoveryProvider()
+        {
+            var provider = KubernetesProviderFactory.Get(_provider, new ServiceProviderConfiguration("kube", "localhost", 443, "", "", 1,"dev"), "");
+            provider.ShouldBeOfType<Kube>();
+        }
+    }
+}