Lint attributes currently don't work for marker lints

[xFrednet]

Extracted from #189:

I tried everything I could think of, but #[allow(...)] doesn't work in any possible way. Here was my last non-working try

#![feature(register_tool)]
#![register_tool(marker)]

fn main() {
    let path = std::path::Path::new("foo.txt");

    #[allow(marker::to_string_on_cow_str)]
    let _ = path.to_string_lossy().to_string();
}

[...]

The lint is not ignored, it's always reported when I run cargo marker

Marker version 0.1.1