Update docs a bit

README.md

@@ -18,19 +18,20 @@ In terms of imports:
 extern crate jsonwebtoken as jwt;
 extern crate rustc_serialize;
 
-use jwt::{encode, decode, Algorithm};
+use jwt::{encode, decode, Header, Algorithm};
 ```
 
 ### Encoding
 ```rust
-let token = encode(&my_claims, "secret", Algorithm::HS256);
+let token = encode(&my_claims, "secret".as_ref(), Header::default()).unwrap();
 ```
 In that example, `my_claims` is an instance of the Claims struct.  
 The struct you are using for your claims should derive `RustcEncodable` and `RustcDecodable`.
 
 ### Decoding
 ```rust
-let claims = decode::<Claims>(&token, "secret", Algorithm::HS256);
+let token = decode::<Claims>(&token, "secret", Algorithm::HS256).unwrap();
+// token is a struct with 2 params: header and claims
 ```
 In addition to the normal base64/json decoding errors, `decode` can return two custom errors:
 
@@ -42,12 +43,19 @@ In addition to the normal base64/json decoding errors, `decode` can return two c
 Right now, the library only validates the algorithm type used but does not verify claims such as expiration.
 Feel free to add a `validate` method to your claims struct to handle that.
 
+### Custom headers
+All the parameters from the RFC are supported but the default header only has `typ` and `alg` set: all the other fields are optional.
+If you want to set the `kid` parameter for example:
+
+```rust
+let mut header = Header::default();
+header.kid = Some("blabla".to_owned());
+let token = encode(&my_claims, "secret".as_ref(), header).unwrap();
+```
+
 ## Algorithms
 Right now, only SHA family is supported: SHA256, SHA384 and SHA512.
 
-## Missing
-The header is currently not customisable and therefore does not support things like kid right now.
-
 ## Performance
 On my thinkpad 440s for a 2 claims struct using SHA256: