Update README and bump to v2.2.0

Author: robertdimarco

README.md

@@ -64,6 +64,11 @@ $decoded = JWT::decode($jwt, $key, array('HS256'));
 Changelog
 ---------
 
+#### 2.2.0 / 2015-06-22
+- Add support for adding custom, optional JWT headers to `JWT::encode()`. See
+[#53](https://github.com/firebase/php-jwt/pull/53/files) for details. Thanks to
+[@mcocaro](https://github.com/mcocaro)!
+
 #### 2.1.0 / 2015-05-20
 - Add support for adding a leeway to `JWT:decode()` that accounts for clock skew
 between signing and verifying entities. Thanks to [@lcabral](https://github.com/lcabral)!

composer.lock

@@ -19,10 +19,10 @@
   <email>operations@firebase.com</email>
   <active>yes</active>
  </lead>
- <date>2015-05-20</date>
+ <date>2015-06-22</date>
  <version>
-  <release>2.1.0</release>
-  <api>2.1.0</api>
+  <release>2.2.0</release>
+  <api>2.2.0</api>
  </version>
  <stability>
   <release>beta</release>