master and latest crates.io version not compiling

[netthier]

The latest version currently on crates.io (0.0.2) does not incorporate PR #5 which is needed to use this crate with a recent compiler, therefore a new version should be pushed to crates.io.
Furthermore, the latest version of syn now requires the extra-traits feature to be enabled for some of the traits used in this crate.
Currently, compilation will fail with errors like:

error[E0277]: `AttrStyle` doesn't implement `Debug`
   --> /home/nett/.cargo/git/checkouts/real-async-trait-rs-99511d8d826cde78/1789be6/src/lib.rs:559:9
    |
559 |         assert_eq!(attr.style, AttrStyle::Outer);
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `AttrStyle` cannot be formatted using `{:?}` because it doesn't implement `Debug`
    |
    = help: the trait `Debug` is not implemented for `AttrStyle`
    = note: this error originates in the macro `assert_eq` (in Nightly builds, run with -Z macro-backtrace for more info)