Explicitly use depdency

Author: xsawyerx

lib/Dancer2/Core/App.pm

@@ -20,6 +20,7 @@ use Plack::Middleware::ConditionalGET;
 
 use Dancer2::Core;
 use Dancer2::Core::Cookie;
+use Dancer2::Core::HTTP;
 use Dancer2::Core::Error;
 use Dancer2::Core::Types;
 use Dancer2::Core::Route;