Add Dockerfile (#277)

* Add Dockerfile
- Added Dockerfile for app
- Made the app a bit shorter
- Improved app with string interpolation usage

* Add trailing CR

* Simplify string joining

samples/dotnetbot/Dockerfile

@@ -0,0 +1,4 @@
+FROM microsoft/dotnet
+COPY bin/Debug/netcoreapp1.0 app
+WORKDIR app
+ENTRYPOINT ["dotnet", "dotnetbot.dll"]

samples/dotnetbot/Program.cs

@@ -1,28 +1,22 @@
 using System;
 
-namespace DotnetBot
+public static class Program
 {
-    public static class Program
-    {
   public static void Main(string[] args) 
   {
-                        string message = "";
+        string message = "Dotnet-bot: Welcome to using .NET Core!";
-                        if (args.Length < 1) 
+          
+        if (args.Length > 0) 
         {
-                          message = "Welcome to .NET Core!";
+          message = String.Join(" ",args);
-                        } else 
-                        {
-                          foreach (string item in args) 
-                          {
-                            message += item; 
-                          }
         }
+
         Console.WriteLine(GetBot(message));
   }
 
   public static string GetBot(string message) 
   {
-                        string bot = "\n" + "        " + message;
+          string bot = $"\n        {message}";
           bot += @"
     __________________
                       \
@@ -66,6 +60,4 @@ namespace DotnetBot
   return bot;
   }
 
-
-        }
 }