JAVA: Update release notes.

java/release_notes.txt

@@ -1,3 +1,12 @@
+July 5th, 2011
+* Code changes
+ - Refactored AreaCodeMap to minimize binary and memory footprint by using 2 different strategies.
+ - Refactored BuildMetadataFromXml.java and added unittests.
+
+* Metadata changes
+ - Regenerate binaries for all existing area code mapping data with smaller sizes.
+ - Added city-level area code data mapping for US and Canada.
+
 June 29th, 2011
 * Code changes
  - Fixed issue 38, issue 39, issue 41 and issue 43