Added support for custom ModuleBase command contexts. Added SocketCommandContext/RpcCommandContext.

src/Discord.Net.Core/Commands/ICommandContext.cs

@@ -0,0 +1,11 @@
+namespace Discord.Commands
+{
+    public interface ICommandContext
+    {
+        IDiscordClient Client { get; }
+        IGuild Guild { get; }
+        IMessageChannel Channel { get; }
+        IUser User { get; }
+        IUserMessage Message { get; }
+    }
+}