[2.2.0rc1] Release preparation

- Updated all component composer.json files to reflect new branch aliases
- Updated changelog
- Updated readme

composer.json

@@ -17,8 +17,8 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "2.1-dev",
-            "dev-develop": "2.2-dev"
+            "dev-master": "2.2-dev",
+            "dev-develop": "2.3-dev"
         }
     },
     "homepage": "https://github.com/zendframework/zend-progress-bar",