Added AddParameter<T>. Fixed AddParameter ignoring default typereaders.

src/Discord.Net.Commands/Builders/CommandBuilder.cs

@@ -80,6 +80,13 @@ namespace Discord.Commands.Builders
             _preconditions.Add(precondition);
             return this;
         }
+        public CommandBuilder AddParameter<T>(string name, Action<ParameterBuilder> createFunc)
+        {
+            var param = new ParameterBuilder(this, name, typeof(T));
+            createFunc(param);
+            _parameters.Add(param);
+            return this;
+        }
         public CommandBuilder AddParameter(string name, Type type, Action<ParameterBuilder> createFunc)
         {
             var param = new ParameterBuilder(this, name, type);

src/Discord.Net.Commands/Builders/ParameterBuilder.cs

@@ -43,10 +43,13 @@ namespace Discord.Commands.Builders
         internal void SetType(Type type)
         {
             var readers = Command.Module.Service.GetTypeReaders(type);
-            if (readers == null)
-                throw new InvalidOperationException($"{type} does not have a TypeReader registered for it");
-            
-            TypeReader = readers.FirstOrDefault().Value;
+            if (readers != null)
+                TypeReader = readers.FirstOrDefault().Value;
+            else
+                TypeReader = Command.Module.Service.GetDefaultTypeReader(type);
+
+            if (TypeReader == null)
+                throw new InvalidOperationException($"{type} does not have a TypeReader registered for it");            
 
             if (type.GetTypeInfo().IsValueType)
                 DefaultValue = Activator.CreateInstance(type);