0.4.0-alpha.11

• Changed #[pinned_drop] to trait implementation.

  #[pinned_drop]
  impl<T> PinnedDrop for Foo<'_, T> {
      fn drop(mut self: Pin<&mut Self>) {
          **self.project().was_dropped = true;
      }
  }

• Added some examples and generated code.

• Improve error messages.