trunk-tracking: merge changes in from master:

* release: prepare 1.7.30.3
* Don't call chown() when initializing config dirs unless owner != worker user.
* Update README.md
* release: build against backported change
* release: udpate version number 1.7.30.3 to 1.7.30.4

config

@@ -27,8 +27,8 @@ if [ "$mod_pagespeed_dir" = "unset" ] ; then
     echo "   You need to separately download the pagespeed library:"
     echo ""
     echo "     $ cd /path/to/ngx_pagespeed"
-    echo "     $ wget https://dl.google.com/dl/page-speed/psol/1.7.30.2.tar.gz"
-    echo "     $ tar -xzvf 1.7.30.2.tar.gz # expands to psol/"
+    echo "     $ wget https://dl.google.com/dl/page-speed/psol/1.7.30.4.tar.gz"
+    echo "     $ tar -xzvf 1.7.30.4.tar.gz # expands to psol/"
     echo ""
     echo "   Or see the installation instructions:"
     echo "     https://github.com/pagespeed/ngx_pagespeed#how-to-build"