Refactoring and fixed a few stylecop errors

src/Discord.Net.Commands/CommandService.Events.cs

@@ -2,7 +2,7 @@
 
 namespace Discord.Commands
 {
-	public class CommandEventArgs
+	public class CommandEventArgs : EventArgs
 	{
 		private readonly string[] _args;
 

src/Discord.Net.Commands/CommandService.cs

@@ -7,7 +7,7 @@ using System.Threading.Tasks;
 namespace Discord.Commands
 {
 	/// <summary> A Discord.Net client with extensions for handling common bot operations like text commands. </summary>
-	public partial class CommandService : IService
+	public sealed partial class CommandService : IService
     {
 		private const string DefaultPermissionError = "You do not have permission to access this command.";