refactor all to async/await (#617)

Co-authored-by: Danny Browning <danny.browning@protectwise.com>
Co-authored-by: Daniel Eades <danieleades@hotmail.com>

src/dns.rs

@@ -47,7 +47,7 @@ impl TrustDnsResolver {
 
 impl hyper_dns::Resolve for TrustDnsResolver {
     type Addrs = vec::IntoIter<IpAddr>;
-    type Future = Box<dyn Future<Item = Self::Addrs, Error = io::Error> + Send>;
+    type Future = Box<dyn Future<Output = Result<Self::Addrs, io::Error>> + Send>;
 
     fn resolve(&self, name: hyper_dns::Name) -> Self::Future {
         let inner = self.inner.clone();