feat(http): add optional serialization of common types via serde

This is behind a Cargo feature to avoid forcing downstream users to
depend on `serde`. It is needed for Servo IPC to work.

src/method.rs

@@ -7,6 +7,9 @@ use error::Error;
 use self::Method::{Options, Get, Post, Put, Delete, Head, Trace, Connect, Patch,
                    Extension};
 
+#[cfg(feature = "serde-serialization")]
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+
 /// The Request Method (VERB)
 ///
 /// Currently includes 8 variants representing the 8 methods defined in
@@ -125,6 +128,21 @@ impl fmt::Display for Method {
     }
 }
 
+#[cfg(feature = "serde-serialization")]
+impl Serialize for Method {
+    fn serialize<S>(&self, serializer: &mut S) -> Result<(), S::Error> where S: Serializer {
+        format!("{}", self).serialize(serializer)
+    }
+}
+
+#[cfg(feature = "serde-serialization")]
+impl Deserialize for Method {
+    fn deserialize<D>(deserializer: &mut D) -> Result<Method, D::Error> where D: Deserializer {
+        let string_representation: String = try!(Deserialize::deserialize(deserializer));
+        Ok(FromStr::from_str(&string_representation[..]).unwrap())
+    }
+} 
+
 #[cfg(test)]
 mod tests {
     use std::collections::HashMap;