add IUptimeClient interface

UptimeSharp/IUptimeClient.cs

@@ -0,0 +1,11 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace UptimeSharp
+{
+  public interface IUptimeClient
+  {
+  }
+}

UptimeSharp/UptimeClient.cs

@@ -5,7 +5,7 @@ using System.Text;
 
 namespace UptimeSharp
 {
-  class UptimeClient
+  public class UptimeClient : IUptimeClient
   {
   }
 }