Update CHANGELOG.md

CHANGELOG.md

@@ -3,6 +3,10 @@
 ###### 0.7.3
  - Add support to Valve style rcon authentication
  - Change maximum packet size to correct value (4096 -> 4106)
+ - Print auth failed message to stderr instead of stdout
+ - Fail immediately if received packet size is out of spec
+ - Return proper exit code from run_terminal_mode()
+ - Add error messages to rcon_command() function
  
 ###### 0.7.2
  - Quit gracefully when Ctrl-D or Ctrl+C is pressed