update changelog for handling invalid session names

Author: tony

CHANGES

@@ -4,6 +4,10 @@ Changelog
 
 Here you can find the recent changes to tmuxp
 
+- :release:`1.2.1 <2016-09-16>`
+- :bug:`132` Handle cases with invalid session names
+- :support:`- backported` update libtmux from 0.5.0 to 0.6.0
+
 - :release:`1.2.0 <2016-06-16>`
 - :feature:`65` Ability to specify ``options`` and ``global_options`` via
   configuration. Also you can specify environment variables via that.