puppet: Install yui-compressor on app servers

We have lots of choices for JS / CSS minifier.  This one works fine
and is in Debian.

(imported from commit bb5a05a8e59d0821e746116af0ef7e3c8ad59aaa)

servers/puppet/manifests/site.pp

@@ -211,7 +211,8 @@ class humbug_apache_base {
 
 class humbug_app_frontend {
   $web_packages = [ "nginx", "memcached", "python-pylibmc", "python-tornado", "python-django",
-                    "python-pygments", "python-flup", "ipython", "python-psycopg2", ]
+                    "python-pygments", "python-flup", "ipython", "python-psycopg2",
+                    "yui-compressor", ]
   package { $web_packages: ensure => "installed" }
   file { "/etc/nginx/nginx.conf":
     require => Package[nginx],