Implement Display for Referer (#122)

Based on #95, but just adds impl Display

src/common/referer.rs

@@ -1,6 +1,7 @@
+use std::fmt;
 use std::str::FromStr;
 
-use http::header::HeaderValue;
+use util::HeaderValueString;
 
 /// `Referer` header, defined in
 /// [RFC7231](http://tools.ietf.org/html/rfc7231#section-5.5.2)
@@ -30,7 +31,7 @@ use http::header::HeaderValue;
 /// let r = Referer::from_static("/People.html#tim");
 /// ```
 #[derive(Debug, Clone, PartialEq)]
-pub struct Referer(HeaderValue);
+pub struct Referer(HeaderValueString);
 
 derive_header! {
     Referer(_),
@@ -44,7 +45,7 @@ impl Referer {
     ///
     /// Panics if the string is not a legal header value.
     pub fn from_static(s: &'static str) -> Referer {
-        Referer(HeaderValue::from_static(s))
+        Referer(HeaderValueString::from_static(s))
     }
 }
 
@@ -53,8 +54,14 @@ error_type!(InvalidReferer);
 impl FromStr for Referer {
     type Err = InvalidReferer;
     fn from_str(src: &str) -> Result<Self, Self::Err> {
-        HeaderValue::from_str(src)
+        HeaderValueString::from_str(src)
             .map(Referer)
             .map_err(|_| InvalidReferer { _inner: () })
     }
 }
+
+impl fmt::Display for Referer {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(&self.0, f)
+    }
+}