Implement Error, Display for Error enum

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "medallion"
-version = "2.0.1"
+version = "2.0.2"
 authors = ["Thomas Gideon <cmdln@thecommandline.net>"]
 description = "JWT library for rust using serde, serde_json and openssl"
 homepage = "http://github.com/commandline/medallion"

src/error.rs

@@ -1,18 +1,53 @@
 use base64::Base64Error;
 use serde_json;
+use std::error;
+use std::fmt;
 use std::string::FromUtf8Error;
 use openssl::error::ErrorStack;
 
 #[derive(Debug)]
 pub enum Error {
-    Format,
+    Custom(String),
     Utf8(FromUtf8Error),
     Base64(Base64Error),
     JSON(serde_json::Error),
-    Custom(String),
     Crypto(ErrorStack),
 }
 
+impl error::Error for Error {
+    fn description(&self) -> &str {
+        match *self {
+            Error::Custom(ref message) => &message,
+            Error::Utf8(ref err) => err.description(),
+            Error::Base64(ref err) => err.description(),
+            Error::JSON(ref err) => err.description(),
+            Error::Crypto(ref err) => err.description(),
+        }
+    }
+
+    fn cause(&self) -> Option<&error::Error> {
+        match *self {
+            Error::Custom(_) => None,
+            Error::Utf8(ref err) => Some(err),
+            Error::Base64(ref err) => Some(err),
+            Error::JSON(ref err) => Some(err),
+            Error::Crypto(ref err) => Some(err),
+        }
+    }
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            Error::Custom(ref message) => f.write_str(&message),
+            Error::Utf8(ref err) => err.fmt(f),
+            Error::Base64(ref err) => err.fmt(f),
+            Error::JSON(ref err) => err.fmt(f),
+            Error::Crypto(ref err) => err.fmt(f),
+        }
+    }
+}
+
 macro_rules! error_wrap {
     ($f: ty, $e: expr) => {
         impl From<$f> for Error {