Update CHANGES.rst with missing changes

CHANGES.rst

 Changes in synapse v0.7.1 (2015-02-19)
 ======================================
 
+* Initial alpha implementation of parts of the Application Services API.
+  Including:
+
+  - AS Registration / Unregistration
+  - User Query API
+  - Room Alias Query API
+  - Push transport for receiving events.
+  - User/Alias namespace admin control
+
 * Add cache when fetching events from remote servers to stop repeatedly
   fetching events with bad signatures.
 * Respect the per remote server retry scheme when fetching both events and