Update release date for 1.0-beta4.

RELEASE.md

@@ -1,7 +1,7 @@
 Release notes
 =================
 
-1.0-beta4 (TBA)
+1.0-beta4 (2015-04-22)
 -------------------------------------------------------------------------------
 * The version of CakePHP bundled with the pre-built package has been updated to version 2.6.3.
 * There ARE database schema changes in this version.  You'll need to run migrations to upgrade an existing installation.  If you don't have command line access to PHP, you can use app/Config/Migration/sql/upgrade_1.0-beta3_to_1.0-beta4.sql to make the appropriate schema changes.