DOC: mention in the readme that 1.9 is a stable version now

It's going to happen soon :-)

INSTALL

@@ -1,15 +1,16 @@
 Installation instructions for HAProxy
 =====================================
 
-This is a development version, so it is expected to break from time to time,
-to add and remove features without prior notification and it should not be used
-in production. If you are not used to build from sources or if you are not used
-to follow updates then it is recommended that instead you use the packages
-provided by your software vendor or Linux distribution. Most of them are taking
-this task seriously and are doing a good job at backporting important fixes. If
-for any reason you'd prefer to use a different version than the one packaged
-for your system, you want to be certain to have all the fixes or to get some
-commercial support, other choices are available at http://www.haproxy.com/.
+This version is a stable version, which means that it belongs to a branch which
+will get some fixes for bugs as they are discovered. Versions which include the
+suffix "-dev" are development versions and should be avoided in production. If
+you are not used to build from sources or if you are not used to follow updates
+then it is recommended that instead you use the packages provided by your
+software vendor or Linux distribution. Most of them are taking this task
+seriously and are doing a good job at backporting important fixes. If for any
+reason you'd prefer a different version than the one packaged for your system,
+you want to be certain to have all the fixes or to get some commercial support,
+other choices are available at http://www.haproxy.com/.
 
 
 Areas covered in this document