Changed version number to 1.3.15

Changed for library
diff --git a/ChangeLog b/ChangeLog
index 18f1c92..bf31b70 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,6 @@
 mbed TLS ChangeLog (Sorted per branch, date)
 
-= mbed TLS 1.3.15 released 2015-10-xx
+= mbed TLS 1.3.15 released 2015-11-04
 
 Security
    * Fix potential double free if ssl_set_psk() is called more than once and