merge README.md

README.md

@@ -20,5 +20,22 @@ API
   * checkKeypair(opts, cb)
   * setKeypair(opts, keypair, cb)
   * check(opts, cb)
-  * set(opts, reg, cb)
+  * set(opts, certs, cb)
 ```
+
+Keypairs
+--------
+
+For convenience, the keypair object will always contain **both** PEM and JWK
+versions of the private and/or public keys when being passed to the `*Keypair` functions.
+
+**set**
+
+`setKeypair` will always be called with `email` and **all three** forms of the keypair:
+`privateKeyPem`, `publicKeyPem`, and `privateKeyJwk`. It's easy to generate `publicKeyJwk`
+from `privateKeyJwk` because it is just a copy of the public fields `e` and `n`.
+
+**check**
+
+`checkKeypair` may be called with any of `email`, `accountId`, and `keypair` - which will
+contain only `publicKeyPem` and `publicKeyJwk`.