Fix clippy lints (#387)

src/error.rs

@@ -180,10 +180,9 @@ impl error::Error for Error {
 
 impl error::Error for Transport {
     fn source(&self) -> Option<&(dyn error::Error + 'static)> {
-        match &self.source {
-            Some(s) => Some(s.as_ref()),
-            None => None,
-        }
+        self.source
+            .as_ref()
+            .map(|s| s.as_ref() as &(dyn error::Error + 'static))
     }
 }
 

src/stream.rs

@@ -397,11 +397,7 @@ pub(crate) fn connect_host(unit: &Unit, hostname: &str, port: u16) -> Result<Tcp
         return Err(ErrorKind::Dns.msg(&format!("No ip address for {}", hostname)));
     }
 
-    let proto = if let Some(ref proxy) = proxy {
-        Some(proxy.proto)
-    } else {
-        None
-    };
+    let proto = proxy.as_ref().map(|proxy| proxy.proto);
 
     let mut any_err = None;
     let mut any_stream = None;