Updated ruby rails version number to 2.3.15

Run 'gem cleanup' after puppet run to remove the old version.

ruby/manifests/init.pp

@@ -52,7 +52,7 @@ class ruby::rails {
             } else {
                 require ruby::rubygems
                 package { "rubygem-rails":
-                    ensure   => "2.3.14",
+                    ensure   => "2.3.15",
                     name     => "rails",
                     provider => "gem",
                 }