Add release entry for 7.7.2.0 to readme

Author: bingbing8

README

@@ -1,3 +1,6 @@
 As of Nov 1st 2016, active development on "Windows for OpenSSH" is being done in https://github.com/PowerShell/openssh-portable. 
 
-This repo (https://github.com/PowerShell/Win32-OpenSSH) is being maintained to keep track of releases and issues.
+This repo (https://github.com/PowerShell/Win32-OpenSSH) is being maintained to keep track of releases and issues.
+
+Release Histroy:
+7/26/2018 -- Release 7.7.2.0 with source https://github.com/PowerShell/openssh-portable/releases/tag/v7.7.2.0