Merge pull request #57 from drichard/patch-1

Update README to document the headers option.

Author: jfromaniello

Diff for: README.md

@@ -30,11 +30,14 @@ encoded private key for RSA and ECDSA.
 * `subject`
 * `issuer`
 * `noTimestamp`
+* `headers`
 
 If `payload` is not a buffer or a string, it will be coerced into a string
 using `JSON.stringify`.
 
-If any `expiresInMinutes`, `audience`, `subject`, `issuer` are not provided, there is no default. The  jwt generated won't include those properties in the payload.
+If any `expiresInMinutes`, `audience`, `subject`, `issuer` are not provided, there is no default. The jwt generated won't include those properties in the payload.
+
+Additional headers can be provided via the `headers` object.
 
 Generated jwts will include an `iat` claim by default unless `noTimestamp` is specified.