default: Better usage of the default Trait

src/crypto.rs

@@ -112,3 +112,9 @@ pub fn verify(signature: &str, signing_input: &str, key: &[u8], algorithm: Algor
         Algorithm::RS512 => verify_rsa(&signature::RSA_PKCS1_2048_8192_SHA512, signature, signing_input, key),
     }
 }
+
+impl Default for Algorithm {
+    fn default() -> Self {
+        Algorithm::HS256
+    }
+}

src/header.rs

@@ -56,8 +56,8 @@ impl Header {
 }
 
 impl Default for Header {
-    /// Returns a JWT header using HS256
-    fn default() -> Header {
-        Header::new(Algorithm::HS256)
+    /// Returns a JWT header using the default Algorithm, HS256
+    fn default() -> Self {
+        Header::new(Algorithm::default())
     }
 }