Issues

Two levels of type erasure when callable is a task

When task is wrapped in queued_task it results with two levels of type erasure. First is inside task through the use of std::function and the second one comes from the use of callable. Could this be simplified somehow (but w/o breaking the requirements)?

The same price is paid even when someone passes simple std::function<void()> into a queued_task as it will also be wrapped in callable. This should be fixed (see #42)!