Update readme for stable version.

Author: relistan

README.md

@@ -37,7 +37,7 @@ one roll-up commit of all our internal code. But all internal development will
 now be on public GitHub. See the CONTRIBUTORS file for the contributors to the
 original internal project.
 
-The **current stable release** is 1.6.0.
+The **current stable release** is 1.8.0.
 
 Installation
 ------------